Incident Commander Now Provides Time Zone Select Menu For Slack Message Rendering
The first several iterations of Incident Commander hard-coded the Slack message rendering such that it would [attempt] to format times for the EST / EDT time zones. I did this because I use this tool at InVision and that's how we run our incidents - in East Coast time. But, in order to make Incident Commander more broadly applicable, there is now a time zone Select menu that allows you to choose which time zone should be used to format the Slack message (though, it still defaults to EST to make it easier for my team).
Run the Incident Commander application on GitHub.
View the Incident Commander code in my Incident Commander project on GitHub.
If you've ever worked with time zones, you know that it's fairly frustrating. Not only are there a vast number of time zones; but, support for Daylight Saving Time (DST) has changed and shifted throughout history. Not to mention, of course, that it's never easy to convert from one time zone to another (unless that other time zone it UTC).
To get time zones to work in Incident Commander, I had to gather a list of supported time zones. For this app, I scraped the Wikipedia page - List of time zone abbreviations - and then converted it into a TypeScript collection. Within the collection, I manually translated the offset of each time zone to be a minutes-based offset such that it would be consumable by the JavaScript Date object (which currently uses minutes as the unit in .getTimezoneOffset()):
export interface Timezone {
abbreviation: string;
name: string;
utc: string;
offset: number;
}
export var timezones: Timezone[] = [
{
abbreviation: "ACDT",
name: "Australian Central Daylight Savings Time",
utc: "UTC+10:30",
offset: -630
},
{
abbreviation: "ACST",
name: "Australian Central Standard Time",
utc: "UTC+09:30",
offset: -570
},
{
abbreviation: "ACT",
name: "Acre Time",
utc: "UTC-05",
offset: 300
},
{
abbreviation: "ADT",
name: "Atlantic Daylight Time",
utc: "UTC-03",
offset: 180
},
{
abbreviation: "AEDT",
name: "Australian Eastern Daylight Savings Time",
utc: "UTC+11",
offset: -660
},
{
abbreviation: "AEST",
name: "Australian Eastern Standard Time",
utc: "UTC+10",
offset: -60600
},
{
abbreviation: "AFT",
name: "Afghanistan Time",
utc: "UTC+04:30",
offset: -270
},
{
abbreviation: "AKDT",
name: "Alaska Daylight Time",
utc: "UTC-08",
offset: 480
},
{
abbreviation: "AKST",
name: "Alaska Standard Time",
utc: "UTC-09",
offset: 540
},
{
abbreviation: "AMST",
name: "Amazon Summer Time (Brazil)",
utc: "UTC-03",
offset: 180
},
{
abbreviation: "AMT",
name: "Amazon Time (Brazil)",
utc: "UTC-04",
offset: 240
},
{
abbreviation: "AMT",
name: "Armenia Time",
utc: "UTC+04",
offset: -240
},
{
abbreviation: "ART",
name: "Argentina Time",
utc: "UTC-03",
offset: 180
},
{
abbreviation: "AST",
name: "Arabia Standard Time",
utc: "UTC+03",
offset: -180
},
{
abbreviation: "AST",
name: "Atlantic Standard Time",
utc: "UTC-04",
offset: 240
},
{
abbreviation: "AWST",
name: "Australian Western Standard Time",
utc: "UTC+08",
offset: -480
},
{
abbreviation: "AZOST",
name: "Azores Summer Time",
utc: "UTC+00",
offset: 0
},
{
abbreviation: "AZOT",
name: "Azores Standard Time",
utc: "UTC-01",
offset: 60
},
{
abbreviation: "AZT",
name: "Azerbaijan Time",
utc: "UTC+04",
offset: -240
},
{
abbreviation: "BDT",
name: "Brunei Time",
utc: "UTC+08",
offset: -480
},
{
abbreviation: "BIOT",
name: "British Indian Ocean Time",
utc: "UTC+06",
offset: -360
},
{
abbreviation: "BIT",
name: "Baker Island Time",
utc: "UTC-12",
offset: 720
},
{
abbreviation: "BOT",
name: "Bolivia Time",
utc: "UTC-04",
offset: 240
},
{
abbreviation: "BRST",
name: "Brasilia Summer Time",
utc: "UTC-02",
offset: 120
},
{
abbreviation: "BRT",
name: "Brasilia Time",
utc: "UTC-03",
offset: 180
},
{
abbreviation: "BST",
name: "Bangladesh Standard Time",
utc: "UTC+06",
offset: -360
},
{
abbreviation: "BST",
name: "Bougainville Standard Time",
utc: "UTC+11",
offset: -660
},
{
abbreviation: "BTT",
name: "Bhutan Time",
utc: "UTC+06",
offset: -360
},
{
abbreviation: "CAT",
name: "Central Africa Time",
utc: "UTC+02",
offset: -120
},
{
abbreviation: "CCT",
name: "Cocos Islands Time",
utc: "UTC+06:30",
offset: -390
},
{
abbreviation: "CDT",
name: "Central Daylight Time (North America)",
utc: "UTC-05",
offset: 300
},
{
abbreviation: "CDT",
name: "Cuba Daylight Time",
utc: "UTC-04",
offset: 240
},
{
abbreviation: "CEST",
name: "Central European Summer Time (Cf. HAEC)",
utc: "UTC+02",
offset: -120
},
{
abbreviation: "CET",
name: "Central European Time",
utc: "UTC+01",
offset: -60
},
{
abbreviation: "CHADT",
name: "Chatham Daylight Time",
utc: "UTC+13:45",
offset: -825
},
{
abbreviation: "CHAST",
name: "Chatham Standard Time",
utc: "UTC+12:45",
offset: -765
},
{
abbreviation: "CHOT",
name: "Choibalsan Standard Time",
utc: "UTC+08",
offset: -480
},
{
abbreviation: "CHOST",
name: "Choibalsan Summer Time",
utc: "UTC+09",
offset: -540
},
{
abbreviation: "CHST",
name: "Chamorro Standard Time",
utc: "UTC+10",
offset: -600
},
{
abbreviation: "CHUT",
name: "Chuuk Time",
utc: "UTC+10",
offset: -600
},
{
abbreviation: "CIST",
name: "Clipperton Island Standard Time",
utc: "UTC-08",
offset: 480
},
{
abbreviation: "CIT",
name: "Central Indonesia Time",
utc: "UTC+08",
offset: -480
},
{
abbreviation: "CKT",
name: "Cook Island Time",
utc: "UTC-10",
offset: 600
},
{
abbreviation: "CLST",
name: "Chile Summer Time",
utc: "UTC-03",
offset: 180
},
{
abbreviation: "CLT",
name: "Chile Standard Time",
utc: "UTC-04",
offset: 240
},
{
abbreviation: "COST",
name: "Colombia Summer Time",
utc: "UTC-04",
offset: 240
},
{
abbreviation: "COT",
name: "Colombia Time",
utc: "UTC-05",
offset: 300
},
{
abbreviation: "CST",
name: "Central Standard Time (North America)",
utc: "UTC-06",
offset: 360
},
{
abbreviation: "CST",
name: "China Standard Time",
utc: "UTC+08",
offset: -480
},
{
abbreviation: "ACST",
name: "Central Standard Time (Australia)",
utc: "UTC+09:30",
offset: -570
},
{
abbreviation: "ACDT",
name: "Central Summer Time (Australia)",
utc: "UTC+10:30",
offset: -630
},
{
abbreviation: "CST",
name: "Cuba Standard Time",
utc: "UTC-05",
offset: 300
},
{
abbreviation: "CT",
name: "China time",
utc: "UTC+08",
offset: -480
},
{
abbreviation: "CVT",
name: "Cape Verde Time",
utc: "UTC-01",
offset: 60
},
{
abbreviation: "CWST",
name: "Central Western Standard Time (Australia) unofficial",
utc: "UTC+08:45",
offset: -525
},
{
abbreviation: "CXT",
name: "Christmas Island Time",
utc: "UTC+07",
offset: -420
},
{
abbreviation: "DAVT",
name: "Davis Time",
utc: "UTC+07",
offset: -420
},
{
abbreviation: "DDUT",
name: "Dumont d'Urville Time",
utc: "UTC+10",
offset: -600
},
{
abbreviation: "DFT",
name: "AIX specific equivalent of Central European Time",
utc: "UTC+01",
offset: -60
},
{
abbreviation: "EASST",
name: "Easter Island Summer Time",
utc: "UTC-05",
offset: 300
},
{
abbreviation: "EAST",
name: "Easter Island Standard Time",
utc: "UTC-06",
offset: 360
},
{
abbreviation: "EAT",
name: "East Africa Time",
utc: "UTC+03",
offset: -180
},
{
abbreviation: "ECT",
name: "Eastern Caribbean Time (does not recognize DST)",
utc: "UTC-04",
offset: 240
},
{
abbreviation: "ECT",
name: "Ecuador Time",
utc: "UTC-05",
offset: 300
},
{
abbreviation: "EDT",
name: "Eastern Daylight Time (North America)",
utc: "UTC-04",
offset: 240
},
{
abbreviation: "AEDT",
name: "Eastern Summer Time (Australia)",
utc: "UTC+11",
offset: -660
},
{
abbreviation: "EEST",
name: "Eastern European Summer Time",
utc: "UTC+03",
offset: -180
},
{
abbreviation: "EET",
name: "Eastern European Time",
utc: "UTC+02",
offset: -120
},
{
abbreviation: "EGST",
name: "Eastern Greenland Summer Time",
utc: "UTC+00",
offset: 0
},
{
abbreviation: "EGT",
name: "Eastern Greenland Time",
utc: "UTC-01",
offset: 60
},
{
abbreviation: "EIT",
name: "Eastern Indonesian Time",
utc: "UTC+09",
offset: -540
},
{
abbreviation: "EST",
name: "Eastern Standard Time (North America)",
utc: "UTC-05",
offset: 300
},
{
abbreviation: "AEST",
name: "Eastern Standard Time (Australia)",
utc: "UTC+10",
offset: -600
},
{
abbreviation: "FET",
name: "Further-eastern European Time",
utc: "UTC+03",
offset: -180
},
{
abbreviation: "FJT",
name: "Fiji Time",
utc: "UTC+12",
offset: -720
},
{
abbreviation: "FKST",
name: "Falkland Islands Summer Time",
utc: "UTC-03",
offset: 180
},
{
abbreviation: "FKT",
name: "Falkland Islands Time",
utc: "UTC-04",
offset: 240
},
{
abbreviation: "FNT",
name: "Fernando de Noronha Time",
utc: "UTC-02",
offset: 120
},
{
abbreviation: "GALT",
name: "Galapagos Time",
utc: "UTC-06",
offset: 360
},
{
abbreviation: "GAMT",
name: "Gambier Islands",
utc: "UTC-09",
offset: 540
},
{
abbreviation: "GET",
name: "Georgia Standard Time",
utc: "UTC+04",
offset: -240
},
{
abbreviation: "GFT",
name: "French Guiana Time",
utc: "UTC-03",
offset: 180
},
{
abbreviation: "GILT",
name: "Gilbert Island Time",
utc: "UTC+12",
offset: -720
},
{
abbreviation: "GIT",
name: "Gambier Island Time",
utc: "UTC-09",
offset: 540
},
{
abbreviation: "GMT",
name: "Greenwich Mean Time",
utc: "UTC+00",
offset: 0
},
{
abbreviation: "GST",
name: "South Georgia and the South Sandwich Islands",
utc: "UTC-02",
offset: 120
},
{
abbreviation: "GST",
name: "Gulf Standard Time",
utc: "UTC+04",
offset: -240
},
{
abbreviation: "GYT",
name: "Guyana Time",
utc: "UTC-04",
offset: 240
},
{
abbreviation: "HADT",
name: "Hawaii-Aleutian Daylight Time",
utc: "UTC-09",
offset: 540
},
{
abbreviation: "HAEC",
name: "Heure Avancee d'Europe Centrale francised name for CEST",
utc: "UTC+02",
offset: -120
},
{
abbreviation: "HAST",
name: "Hawaii-Aleutian Standard Time",
utc: "UTC-10",
offset: 600
},
{
abbreviation: "HKT",
name: "Hong Kong Time",
utc: "UTC+08",
offset: -480
},
{
abbreviation: "HMT",
name: "Heard and McDonald Islands Time",
utc: "UTC+05",
offset: -300
},
{
abbreviation: "HOVST",
name: "Khovd Summer Time",
utc: "UTC+08",
offset: -480
},
{
abbreviation: "HOVT",
name: "Khovd Standard Time",
utc: "UTC+07",
offset: -420
},
{
abbreviation: "ICT",
name: "Indochina Time",
utc: "UTC+07",
offset: -420
},
{
abbreviation: "IDT",
name: "Israel Daylight Time",
utc: "UTC+03",
offset: -180
},
{
abbreviation: "IOT",
name: "Indian Ocean Time",
utc: "UTC+03",
offset: -180
},
{
abbreviation: "IRDT",
name: "Iran Daylight Time",
utc: "UTC+04:30",
offset: -270
},
{
abbreviation: "IRKT",
name: "Irkutsk Time",
utc: "UTC+08",
offset: -480
},
{
abbreviation: "IRST",
name: "Iran Standard Time",
utc: "UTC+03:30",
offset: -210
},
{
abbreviation: "IST",
name: "Indian Standard Time",
utc: "UTC+05:30",
offset: -330
},
{
abbreviation: "IST",
name: "Irish Standard Time",
utc: "UTC+01",
offset: -60
},
{
abbreviation: "IST",
name: "Israel Standard Time",
utc: "UTC+02",
offset: -120
},
{
abbreviation: "JST",
name: "Japan Standard Time",
utc: "UTC+09",
offset: -540
},
{
abbreviation: "KGT",
name: "Kyrgyzstan time",
utc: "UTC+06",
offset: -360
},
{
abbreviation: "KOST",
name: "Kosrae Time",
utc: "UTC+11",
offset: -660
},
{
abbreviation: "KRAT",
name: "Krasnoyarsk Time",
utc: "UTC+07",
offset: -420
},
{
abbreviation: "KST",
name: "Korea Standard Time",
utc: "UTC+09",
offset: -540
},
{
abbreviation: "LHST",
name: "Lord Howe Standard Time",
utc: "UTC+10:30",
offset: -630
},
{
abbreviation: "LHST",
name: "Lord Howe Summer Time",
utc: "UTC+11",
offset: -660
},
{
abbreviation: "LINT",
name: "Line Islands Time",
utc: "UTC+14",
offset: -840
},
{
abbreviation: "MAGT",
name: "Magadan Time",
utc: "UTC+12",
offset: -720
},
{
abbreviation: "MART",
name: "Marquesas Islands Time",
utc: "UTC-09:30",
offset: 570
},
{
abbreviation: "MAWT",
name: "Mawson Station Time",
utc: "UTC+05",
offset: -300
},
{
abbreviation: "MDT",
name: "Mountain Daylight Time (North America)",
utc: "UTC-06",
offset: 360
},
{
abbreviation: "MET",
name: "Middle European Time Same zone as CET",
utc: "UTC+01",
offset: -60
},
{
abbreviation: "MEST",
name: "Middle European Summer Time Same zone as CEST",
utc: "UTC+02",
offset: -120
},
{
abbreviation: "MHT",
name: "Marshall Islands",
utc: "UTC+12",
offset: -720
},
{
abbreviation: "MIST",
name: "Macquarie Island Station Time",
utc: "UTC+11",
offset: -660
},
{
abbreviation: "MIT",
name: "Marquesas Islands Time",
utc: "UTC-09:30",
offset: 570
},
{
abbreviation: "MMT",
name: "Myanmar Standard Time",
utc: "UTC+06:30",
offset: -390
},
{
abbreviation: "MSK",
name: "Moscow Time",
utc: "UTC+03",
offset: -180
},
{
abbreviation: "MST",
name: "Malaysia Standard Time",
utc: "UTC+08",
offset: -480
},
{
abbreviation: "MST",
name: "Mountain Standard Time (North America)",
utc: "UTC-07",
offset: 420
},
{
abbreviation: "MUT",
name: "Mauritius Time",
utc: "UTC+04",
offset: -240
},
{
abbreviation: "MVT",
name: "Maldives Time",
utc: "UTC+05",
offset: -300
},
{
abbreviation: "MYT",
name: "Malaysia Time",
utc: "UTC+08",
offset: -480
},
{
abbreviation: "NCT",
name: "New Caledonia Time",
utc: "UTC+11",
offset: -660
},
{
abbreviation: "NDT",
name: "Newfoundland Daylight Time",
utc: "UTC-02:30",
offset: 150
},
{
abbreviation: "NFT",
name: "Norfolk Time",
utc: "UTC+11",
offset: -660
},
{
abbreviation: "NPT",
name: "Nepal Time",
utc: "UTC+05:45",
offset: -345
},
{
abbreviation: "NST",
name: "Newfoundland Standard Time",
utc: "UTC-03:30",
offset: 210
},
{
abbreviation: "NT",
name: "Newfoundland Time",
utc: "UTC-03:30",
offset: 210
},
{
abbreviation: "NUT",
name: "Niue Time",
utc: "UTC-11",
offset: 660
},
{
abbreviation: "NZDT",
name: "New Zealand Daylight Time",
utc: "UTC+13",
offset: -780
},
{
abbreviation: "NZST",
name: "New Zealand Standard Time",
utc: "UTC+12",
offset: -720
},
{
abbreviation: "OMST",
name: "Omsk Time",
utc: "UTC+06",
offset: -360
},
{
abbreviation: "ORAT",
name: "Oral Time",
utc: "UTC+05",
offset: -300
},
{
abbreviation: "PDT",
name: "Pacific Daylight Time (North America)",
utc: "UTC-07",
offset: 420
},
{
abbreviation: "PET",
name: "Peru Time",
utc: "UTC-05",
offset: 300
},
{
abbreviation: "PETT",
name: "Kamchatka Time",
utc: "UTC+12",
offset: -720
},
{
abbreviation: "PGT",
name: "Papua New Guinea Time",
utc: "UTC+10",
offset: -600
},
{
abbreviation: "PHOT",
name: "Phoenix Island Time",
utc: "UTC+13",
offset: -780
},
{
abbreviation: "PHT",
name: "Philippine Time",
utc: "UTC+08",
offset: -480
},
{
abbreviation: "PKT",
name: "Pakistan Standard Time",
utc: "UTC+05",
offset: -300
},
{
abbreviation: "PMDT",
name: "Saint Pierre and Miquelon Daylight time",
utc: "UTC-02",
offset: 120
},
{
abbreviation: "PMST",
name: "Saint Pierre and Miquelon Standard Time",
utc: "UTC-03",
offset: 180
},
{
abbreviation: "PONT",
name: "Pohnpei Standard Time",
utc: "UTC+11",
offset: -660
},
{
abbreviation: "PST",
name: "Pacific Standard Time (North America)",
utc: "UTC-08",
offset: 480
},
{
abbreviation: "PST",
name: "Philippine Standard Time",
utc: "UTC+08",
offset: -480
},
{
abbreviation: "PYST",
name: "Paraguay Summer Time (South America)",
utc: "UTC-03",
offset: 180
},
{
abbreviation: "PYT",
name: "Paraguay Time (South America)",
utc: "UTC-04",
offset: 240
},
{
abbreviation: "RET",
name: "Reunion Time",
utc: "UTC+04",
offset: -240
},
{
abbreviation: "ROTT",
name: "Rothera Research Station Time",
utc: "UTC-03",
offset: 180
},
{
abbreviation: "SAKT",
name: "Sakhalin Island time",
utc: "UTC+11",
offset: -660
},
{
abbreviation: "SAMT",
name: "Samara Time",
utc: "UTC+04",
offset: -240
},
{
abbreviation: "SAST",
name: "South African Standard Time",
utc: "UTC+02",
offset: -120
},
{
abbreviation: "SBT",
name: "Solomon Islands Time",
utc: "UTC+11",
offset: -660
},
{
abbreviation: "SCT",
name: "Seychelles Time",
utc: "UTC+04",
offset: -240
},
{
abbreviation: "SDT",
name: "Samoa Daylight Time",
utc: "UTC-10",
offset: 600
},
{
abbreviation: "SGT",
name: "Singapore Time",
utc: "UTC+08",
offset: -480
},
{
abbreviation: "SLST",
name: "Sri Lanka Standard Time",
utc: "UTC+05:30",
offset: -330
},
{
abbreviation: "SRET",
name: "Srednekolymsk Time",
utc: "UTC+11",
offset: -660
},
{
abbreviation: "SRT",
name: "Suriname Time",
utc: "UTC-03",
offset: 180
},
{
abbreviation: "SST",
name: "Samoa Standard Time",
utc: "UTC-11",
offset: 660
},
{
abbreviation: "SST",
name: "Singapore Standard Time",
utc: "UTC+08",
offset: -480
},
{
abbreviation: "SYOT",
name: "Showa Station Time",
utc: "UTC+03",
offset: -180
},
{
abbreviation: "TAHT",
name: "Tahiti Time",
utc: "UTC-10",
offset: 600
},
{
abbreviation: "THA",
name: "Thailand Standard Time",
utc: "UTC+07",
offset: -420
},
{
abbreviation: "TFT",
name: "Indian/Kerguelen",
utc: "UTC+05",
offset: -300
},
{
abbreviation: "TJT",
name: "Tajikistan Time",
utc: "UTC+05",
offset: -300
},
{
abbreviation: "TKT",
name: "Tokelau Time",
utc: "UTC+13",
offset: -780
},
{
abbreviation: "TLT",
name: "Timor Leste Time",
utc: "UTC+09",
offset: -540
},
{
abbreviation: "TMT",
name: "Turkmenistan Time",
utc: "UTC+05",
offset: -300
},
{
abbreviation: "TRT",
name: "Turkey Time",
utc: "UTC+03",
offset: -180
},
{
abbreviation: "TOT",
name: "Tonga Time",
utc: "UTC+13",
offset: -780
},
{
abbreviation: "TVT",
name: "Tuvalu Time",
utc: "UTC+12",
offset: -720
},
{
abbreviation: "ULAST",
name: "Ulaanbaatar Summer Time",
utc: "UTC+09",
offset: -540
},
{
abbreviation: "ULAT",
name: "Ulaanbaatar Standard Time",
utc: "UTC+08",
offset: -480
},
{
abbreviation: "USZ1",
name: "Kaliningrad Time",
utc: "UTC+02",
offset: -120
},
{
abbreviation: "UTC",
name: "Coordinated Universal Time",
utc: "UTC+00",
offset: 0
},
{
abbreviation: "UYST",
name: "Uruguay Summer Time",
utc: "UTC-02",
offset: 120
},
{
abbreviation: "UYT",
name: "Uruguay Standard Time",
utc: "UTC-03",
offset: 180
},
{
abbreviation: "UZT",
name: "Uzbekistan Time",
utc: "UTC+05",
offset: -300
},
{
abbreviation: "VET",
name: "Venezuelan Standard Time",
utc: "UTC-04",
offset: 240
},
{
abbreviation: "VLAT",
name: "Vladivostok Time",
utc: "UTC+10",
offset: -600
},
{
abbreviation: "VOLT",
name: "Volgograd Time",
utc: "UTC+04",
offset: -240
},
{
abbreviation: "VOST",
name: "Vostok Station Time",
utc: "UTC+06",
offset: -360
},
{
abbreviation: "VUT",
name: "Vanuatu Time",
utc: "UTC+11",
offset: -660
},
{
abbreviation: "WAKT",
name: "Wake Island Time",
utc: "UTC+12",
offset: -720
},
{
abbreviation: "WAST",
name: "West Africa Summer Time",
utc: "UTC+02",
offset: -120
},
{
abbreviation: "WAT",
name: "West Africa Time",
utc: "UTC+01",
offset: -60
},
{
abbreviation: "WEST",
name: "Western European Summer Time",
utc: "UTC+01",
offset: -60
},
{
abbreviation: "WET",
name: "Western European Time",
utc: "UTC+00",
offset: 0
},
{
abbreviation: "WIT",
name: "Western Indonesian Time",
utc: "UTC+07",
offset: -420
},
{
abbreviation: "WST",
name: "Western Standard Time",
utc: "UTC+08",
offset: -480
},
{
abbreviation: "YAKT",
name: "Yakutsk Time",
utc: "UTC+09",
offset: -540
},
{
abbreviation: "YEKT",
name: "Yekaterinburg Time",
utc: "UTC+05",
offset: -300
}
];
As you can see, the "offset" property of each time zone item reflects what the Date.prototype.getTimezoneOffset() would return if the Date object were created on a host computer running in the given time zone. I did this manually, so hopefully there aren't too many errors.
Once a user selects the desired time zone, I then attempt to format the Slack message to use the associated offset-in-minutes. I say "attempt" because this will likely be error prone in certain conversions at certain times of the year. I'm trying to "fake" being in the selected time zone by adjusting a Date object in the browser's time zone (using the offset minutes). This will cause a problem if the browser's time zone can't actually create the date/time that would otherwise be valid in the target time zone. That said, this may be the best I can do without a massive amount of effort:
// I format the given Date object as a time string in the EST / EDT timezone.
private formatTime( value: Date, timezone: Timezone ) : string {
// In order to [try our best to] convert from the local timezone to the Slack
// timezone for rendering, we're going to use the difference in offset minutes
// to alter a local copy of the Date object.
var offsetDelta = ( timezone.offset - value.getTimezoneOffset() );
// Clone the date so we don't mess up the original value as we adjust it.
var slackDate = new Date( value );
// Attempt to move from the current TZ to the given TZ by adjusting minutes.
slackDate.setMinutes( slackDate.getMinutes() - offsetDelta );
var hours = slackDate.getHours();
var minutes = slackDate.getMinutes();
var period = ( hours < 12 )
? "AM"
: "PM"
;
var normalizedHours = ( ( hours % 12 ) || 12 );
var normalizedMinutes = ( "0" + minutes ).slice( -2 );
return( `${ normalizedHours }:${ normalizedMinutes } ${ period } ${ timezone.abbreviation }` );
}
As you can see, I'm not actually changing a time zone anywhere in the JavaScript / TypeScript. Really, I'm just shifting the minutes in the current date to approximate the corresponding time in the target time zone. If anyone has a better solution, I'm very open to feedback. In the meantime, this should make the Incident Commander much more flexible.
Oh, and the browser will remember your time zone selection across page refreshes using the localStorage API. I wasn't sure if that should be saved with the Incident itself, or just cached locally. I went with a local cache to keep things simple.
Want to use code from this post? Check out the license.
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