#1588 UX issues / errors

[stronnag]

#1588 changed the TZ offset display / input from minutes to hours. This has a few UX inconsistencies.

• The unit is listed as minutes; it is now decimal/fractional hours
• The help text is also incorrect (claims minutes vice decimal/fractional hours)
• As TZ offsets are conventionally standardised as +/-HH:MM it might be clearer to the user to provide a standardised format (and one with which the user may be familiar from e.g. email dates).

Note: there are time zones that are NOT integer hours (e.g. Newfoundland). #1588 accommodates this.