In such an application I wouldn't be to worried about timing accuracy.
Think is your dog going to notice if he is fed 1 minute earlier each
day? Think what would happen if you ate supper exactly one minute
earlier each day then the day before, you would never notice.  (and this
is extremely low accuracy for a pic you should be able to get <1 sec no
trouble).

Now if it's commercial idea I'd make it accurate to less then a sec or
so, if it's for yourself, I guess that's for you to decide (depends on
your personal degree of perfectionism :)

Just my two cents.
Hope it helps,
Aaron

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