There is only one SI unit of time and
that is the *second *(s) but other units are often used.

60
seconds make a minute

60 minutes make an hour

24
hours make a day

7 days make a week

A
*solar *year is the time taken for the Earth to go
round the Sun, and is about 365¼ days. A *calendar *year
must have a whole number of days so is 365 days
for a common year and 366 days for a leap year.
Usually every fourth year is a leap year.

A *calendar *month
has 28 or 29 or 30 or 31 days so is
not a very precise way of measuring time. Scientists and other
people wanting to measure time accurately do not often use calendar
months.

A *lunar *month is the time from the first sighting of one New Moon
to the first sighting of the next and is either twenty nine or thirty days.
Some religions use lunar months.

There is a very much longer article on time and the calendar elsewhere in this web site - to visit it please click here