nedarim 60

measuring time until the end of the cycle that has begun and one is observing.

or

to be at the centre of one's own cycle.

if take a vow not to benefit from something until the end of the day; is that until sunset or 24 hours from making the vow? is time something objective that we observe or something that we construct and create for ourselves?

pesachim 12

who you are determines when you will have breakfast.

but everyone knows when day becomes night