Punctuation in numbers can be very tricky. Numbers can take the form of dates, time, numbers, decimals, etc. Punctuating one of those forms may require the use of many punctuation marks.
Dates
Full stops or slashes are often used in dates.
| American usage | ||
| 12.3.09 | 3/12/09 | |
| 2.28.15 | 2/28/15 | |
Scientific usage
Full stops are not used in scientific abbreviations.
| 12 kg | 50 cm |
Times
Full stops and occasionally colons are used in times.
| 4.15 p.m. | 21.15 |
| 3:30 a.m. | 20:30 |
Long numbers
Commas are used in numbers to mark off units of thousands and millions.
| 1,359 | 2,543,678 |
Decimals
Full stops indicate decimal points.
| 1.5 | 25.08 |