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I think Apple is still doing that: https://developer.apple.com/documentation/foundation/nstimei...

Couple decades ago Microsoft did that too, VT_DATE in old OLE Automation keeping FP64 value inside. Luckily, their newer APIs and frameworks are using uint64 with 100-nanoseconds ticks.

It's very common in games.

Integers are always an option, of course, but in this context it's hard to beat the convenience of just storing seconds in a floating point number.

Don't have a publicly visible reference to give at the moment, but it's still sometimes seen where relative timestamps are being tracked, such as in an audio library tracking time elapsed since start. It's probably less used for absolute time where the precision problems are more obvious.

> int64 epoch microseconds

surely nanoseconds is the truth.

LONG_MAX nanoseconds is just Friday, April 11, 2262 11:47:16.854 PM, not exactly a future-proof approach. I guess having Tuesday, September 21, 1677 12:12:43.145 AM as the earliest expressible timestamp neatly sidesteps the problem of proleptic Gregorian vs Julian calendars.