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Record FAT file timestamps in UTC - #33
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deadprogram merged 1 commit intoOct 13, 2026
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go_fatfs_get_fattime called Date() on the result of time.Now(), which is in the local time zone. To calculate the local date, Date() must load the local time zone. This caused the time zone loader (time.loadTzinfo, time.tzset and related functions) to be included in the binary. In the examples/console/fatfs/machine example on pico2, this increased the binary size by 4,408 bytes of flash. Write all FAT timestamps in UTC. Most microcontrollers do not have a real-time clock, so these timestamps are seldom correct, and a time zone adds no value.
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@deadprogram PTAL. This does change the timezone of the timestamp that is written, or more specifically the TZ offset that is used to compute the fat timestamp, but I argue that as most micro's don't have an RTC, the timestamp they were writing wasn't correct, and using the "local" timezone for that timestamp is equally flawed for a system without an RTC. I argue, without strong supporting evidence, that systems writing files to FAT formatted systems would prefer the 4kb of programs space back -- and probably some heap -- more than they prefer a bike shed about timestamps. |
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Thanks for working on this @davecheney now merging.
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go_fatfs_get_fattime called Date() on the result of time.Now(), which is in the local time zone. To calculate the local date, Date() must load the local time zone. This caused the time zone loader (time.loadTzinfo, time.tzset and related functions) to be included in the binary. In the examples/console/fatfs/machine example on pico2, this increased the binary size by 4,408 bytes of flash.
Write all FAT timestamps in UTC. Most microcontrollers do not have a real-time clock, so these timestamps are seldom correct, and a time zone adds no value.