Thoughts on time and date in applications
I’m making an app that has a chat functionality, and so time is an important factor. I couldn’t find serious discussions about this excepte, “use X format”; So i made this to gather my thoughts about it.
TL;DR
Time and dates are hard!
Why is time important?
You might think that for a simple chat app, there’s no need to use time, but you should always include time. It’s a great way to sort, though this might be acheived by some auto-incremented number.
What DateTime format to use?
There are plenty of libraries to convert time and dates to whatever format you want, so why not just use what you use in your daily life? Let me show you:
Some examples of the same DateTime (seconds an milliseconds omitted, mostly)
| DateTime code | Description | My opinion |
|---|---|---|
| 2012-10-03T12:13:00Z | UTC time friendly | |
| 10-03-12 12:13PM | US/UK short AM/PM | Stupid, because counting 12 + 12 only makes sense when using |
| 10-03-12 12:13 | US/UK short 24H | Internaly sencible, internationally stupid |
| 10-03-2012 12:13PM | US/UK long AM/PM | see above |
| 03-10-12 12:13 | Short international | What I grew up using, but it’s confusing |
| 03-10-2012 12:13 | Long international | The most sencible day-to-day format |
| 2012-10-03 12:13 | Sortable long international | Very useful for sorting |
| 2012-40-3 12:13 | year-week-weekday international | Very useful for class schedules |
| 2012-40-4 12:13 | year-week-weekday US | Who thought it was a good idea to start the week on Sunday? |
| 201210031213 | sortable character safe | Great for document naming or a timestamp on a database-row |
| 100320121213 | non-sortable character safe US | NEVER use this |
| 1349266380 | UNIX time seconds | Somewhat useful |
| 1349259180000 | UNIX time milliseconds | THE best way to use date and time, (see bellow) |
You might be confused by the “snowflaking” of the US in all of this, but it has it’s reasons, mostly the unwillingness to risk confusion among it’s citizens. However the US Military does use the the UTC time,
You might say “hey, how about my country/culture’s calendar? This is awefully eurocentric”, and yes it is completely correct and a good point to make. Here’s some examples of calendars from around the world that is in use today:
| Date | Decription |
|---|---|
| 5773-Tishri-18 | Hebrew |
| 1433-Dhu I-Qa’da-18 | Islamic |
| 1391-Mehr-13 | Persian |
| 1934-Asvina-12 | Indian Civil |
| Dragon-Dog-18 | Chinese variant 1 (not actually used) |
| 4710-8-18 | Chinese variant 2 (China actually use Gregorian) |
there are scores upon scores of others, some only used by tribes in micronesia or in the himalayas, (that there’s probably a conversion for anyway, because developers love a challange, or some social anthropologist needs it in their research
I will not denegrade the non-gregorian calanders, and they are useful for those who share them, but I don’t think I’ll be using Dragon-dog-18, (though if I were, I would have to have some logic to assume it’s the closest Dragon in the last 12 years)
But what about Timezones?
Short answer is: Ignore it, and use a universal time with conversion logic!
Great video about timezones every dev should watch:
Conlusion: Use millisecond UNIX time
The computer counts in this time unit, (.net actually has a unit caller “ticks” that is MUCH smaller)