14.6b Intervals of time.

When intervals of time are expressed by whole numbers, such as 6-7 p.m., only one number sign is needed (unless they are divided between braille lines) —the same way as any other hyphenated numerical expression. However, when two units of time are joined and the first unit consists of hours and minutes, a number sign is required before the second unit. In other words, whenever hours follow minutes, repeat the number sign.

In print, intervals of time are joined either by an en (short) dash or by a hyphen. In braille, always use a hyphen. Regardless of print spacing, no space should be left before or after the braille hyphen. Division between braille lines can be made only following a print hyphen. Examples:

3–4 a.m.6 - 7:12
4:15-5:004:15-5:00
5:15–6