The dash is used between ranges. These are often date ranges. For example:
Between times: 1200–1600
Between times: 6 am–8 am
Between days: Monday–Friday
Between dates: 12–15 October
Between months: June–August
Between years: 1967–1969
The dash can be used for any range. For example:
Note: Your readers will assume these ranges are inclusive; i.e., the ranges include the values that bound the ranges.
Avoid Using Spaces
Avoid putting spaces around your dash. This is not a ruling. It is, however, good practice because when you use spaces, your autocorrect will often try to help you by changing your short dash (especially if you've decided to use hyphens) to an em dash (a longer dash, the length of an uppercase "M"). As autocorrect is inconsistent with this "help," you often end up with a mix of en dashes (a shorter dash, the length of a lowercase "n") and long dashes between your ranges.
Using no spaces at all stops autocorrect trying to help you (as it waits for a space before it looks at what you've just typed), and using no spaces also eliminates inconsistencies with spacing. Here's a scruffy example:
Hyphens are not meant to be used for ranges (e.g., 10-12, 1967-
1971). Dashes are used for this purpose. However, given that the hyphen is so easy to find on a keyboard, hyphens have become acceptable for ranges. Only a very strict grammar pedant would pull you up for using hyphens. If this were to happen, you could make a good case for the pedant being out of date.