"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."
"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."
Debugging test and application code reveals that many errors originate from misunderstandings about time handling. Programmers frequently make incorrect assumptions about calendar systems and computer timekeeping. Common false assumptions include: days always having 24 hours, months having fixed day counts, years always containing 365 days, and 24-hour periods beginning and ending within the same calendar unit. Additional misconceptions involve time zones remaining constant, system clocks always being accurate, and server-client clock synchronization. These assumptions fail to account for daylight savings time, leap years, time zone changes in production environments, clock drift, and distributed system timing discrepancies. Understanding these gotchas is essential for writing reliable time-dependent code.
#time-handling-bugs #calendar-misconceptions #system-clock-synchronization #daylight-savings-time #distributed-systems-timing
Read at infiniteundo.com
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