https://infiniteundo.com/post/25326999628/falsehoods-programmers-believe-about-time

# All of these assumptions are wrong

- There are always 24 hours in a day.

- Months have either 30 or 31 days.

- Years have 365 days.

- February is always 28 days long.

- Any 24-hour period will always begin and end in the same day (or week, or month).

- A week always begins and ends in the same month.

- A week (or a month) always begins and ends in the same year.

- The machine that a program runs on will always be in the GMT time zone.

- Ok, that’s not true. But at least the time zone in which a program has to run will never change.

- Well, surely there will never be a change to the time zone in which a program hast to run in production.

- The system clock will always be set to the correct local time.

- The system clock will always be set to a time that is not wildly different from the correct local time.

- If the system clock is incorrect, it will at least always be off by a consistent number of seconds.

- The server clock and the client clock will always be set to the same time.

- The server clock and the client clock will always be set to around the same time.

- Ok, but the time on the server clock and time on the client clock would never be different by a matter of decades.

- If the server clock and the client clock are not in synch, they will at least always be out of synch by a consistent number of seconds.

- The server clock and the client clock will use the same time zone.

-The system clock will never be set to a time that is in the distant past or the far future.

- Time has no beginning and no end.

-One minute on the system clock has exactly the same duration as one minute on any other clock

- Ok, but the duration of one minute on the system clock will be pretty close to the duration of one minute on most other clocks.

- Fine, but the duration of one minute on the system clock would never be more than an hour.

- You can’t be serious.

- The smallest unit of time is one second.

- Ok, one millisecond.

- It will never be necessary to set the system time to any value other than the correct local time.

- Ok, testing might require setting the system time to a value other than the correct local time but it will never be necessary to do so in production.

- Time stamps will always be specified in a commonly-understood format like 1339972628 or 133997262837.

- Time stamps will always be specified in the same format.

- Time stamps will always have the same level of precision.

- A time stamp of sufficient precision can safely be considered unique.

- A timestamp represents the time that an event actually occurred.

- Human-readable dates can be specified in universally understood formats such as 05/07/11.

#programming #date #time