Units of time are measurements of how long something lasts.

Did you know that a "jiffy" is actually a unit of time?
It is 1/100th of a second.
So when you tell someone you will be ready in a "jiffy",
you had better actually be ready right then.
timeguy
Units of Time
1 minute = 60 seconds

1 hour = 60 minutes

1 hour = 3600 seconds

1 day = 24 hours

1 week = 7 days

1 year = 365 days

1 year = 12 months

1 year = 52 weeks
Mathematics and Time

When adding or subtracting time, the units (hour, minutes, seconds) are treated separately. Adjustments are made when minutes and seconds reach 60, or more.

Addition:
addtime

This same approach would be repeated if the seconds
were also 60 or more.

A similar approach is used for subtracting.
 
Subtraction:
 
sub1

sub2
When subtracting, it may be necessary to "borrow" from hours or minutes to increase the size of the minutes or seconds.

We want to avoid ending up with "negative" time.

It may be necessary to "borrow" to adjust just minutes, or just seconds, or both (as seen in this example). It does not matter which adjustment is made first. This example adjusted minutes first, then seconds.

Final answers should always have minutes < 60 and seconds < 60.

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