Date & Time
Computers follow unique approach to tackle date and time. Instead of keeping date and time into consideration, It follows the Unix Epoch, where we calculate date and time based on timestamps, as someone started a stopwatch on 01–01–1970 at 00.00.00 UTC.
Date.now() // Gives number of milliseconds elapsed from 1st jan, 1970.So How do all computers show same time and are in sync?
- The Hardware Clock, this keeps track of time even when offline.
- OS syncs periodically when connected atomic clocks on Internet, using NTP.
- Programming languages handle raw Unix timestamps and provide time as per context.
For example: A student in India, submit quiz at 5PM evening, server in US, keeps the current time-stamp instead of 5PM.
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The Golden rule is keep the Backend simple storing following Unix Epoch, and frontend do the rest. This Idea is excellent:
- Zero Ambiguity, as the time is completely absolute.
- Insane performance, in calculation or sorting.
- Perfect portability, to various languages.
What if users manipulate timestamps?
- Using backend as ultimate source of truth.
- For high frequency financial trading or legal audits, We can use True Time & Vector Clocks.
- We can also use Network Time APIs.
What if my game is offline and I need accurate time?
In this case, we can apply a simple approach, Instead of storing time, we store timestamps, zero when game started and so on, and sync when there is active Internet connection.
