fluffy rambles

• There are 365 days in a year.
• There are 365.25 days in a year.
• There are 365.24 days in a year.
• There are a fixed number of days in a year.
• Time zones never change.
• There are exactly 24 time zones.
• Okay, there are no more than 48 time zones.
• … Can’t be more than 100, right?
• Well at least time offsets never change.
• Fine, then, UTC never changes.
• … Okay, UTC will never change again.
• Daylight saving happens at the same time for everyone.
• Daylight saving happens at the same time for any given place.
• Daylight saving adjusts by one hour for everyone.
• All time zones are based on whole-hour offsets.
• … Okay, 30 minutes?
• … 15 minutes?
• Well at least we know that all time zones are based on the same offset every day.
• A timestamp means the same thing in retrospect as it does today.
• Any number that can be parsed as a timestamp is a timestamp.
• Adding more precision to a number parsed as a timestamp won’t hurt.
• General relativity doesn’t matter for timekeeping.
• …Special relativity doesn’t matter for timekeeping?
• There are exactly 86400 seconds in every day.
• There are exactly 86400 seconds in most days.
• All seconds are the same length.
• Two devices with the same sampling interval will record the same number of samples within the same time period.
• Two identical devices with the same sampling interval will record the same number of samples within the same time period.
• Two circuits within the same device will record the same number of samples within the same time period.
• All devices have a single global clock.
• All devices with multiple clocks will have those clocks remain in sync.
• All devices with multiple clocks will have those clocks move at a fixed interval relative to one another.
• The reported time on an RTC will always move forward.
• A single CPU with a single RTC will always report time that moves forward.
• A single CPU with a single RTC will always report time that moves forward if it isn’t synchronized to an external source such as NTP or GPS.
• If you synchronize your times via NTP you will never have to worry about clocks drifting.
• If you synchronize your devices via NTP you never have to worry about time moving backwards.
• Highly-precise time can be reported accurately using a CPU’s instruction counter.
• Any two times can be arbitrarily compared using the mathematical greater-than/less-than operator.
• A recorded timestamp that comes after a previous recorded timestamp will always compare as numerically greater.
• All HH:MM:SS-format time stamps go from 00:00:00 thru 23:59:59.
• Timestamps formatted in ISO-8601 can be sorted lexically.
• Timestamps formatted in ISO-8601 and kept within a single timezone can be sorted lexically.
• Timestamps formatted in ISO-8601 and with a single specified UTC offset can be sorted lexically.
• All timekeeping can be performed based on local time.
• All timekeeping can be performed based on UTC.
• All timekeeping can be performed based on storing as UTC and displaying in the local timezone.
• All timekeeping can be done reasonably with a single canonical representation.
• Any single event or item can be stored with a single canonical date.
• Okay, we can use a single date for “authored on” and another one for “last modified”
• It is easy to determine whether something happened in the past based solely on its timestamp
• The concept of “now” is consistent.

And some bonus things where people get confused about time zones in general:

• 2:20 PM PDT is two minutes after 2:18 PM EDT
• The time zone is always called PST even during daylight saving, and scheduling a call for 4:30 PM PST totally makes sense in the middle of June