Honeywell AQ25A Series Technical Reference Booklet page 245

Permanent Backlight
Use this parameter to select whether or not the thermostat's screen is
permanently illuminated. If you do not choose permanent backlight,
the screen will lit for 12 seconds when any button is pressed.
Time Display Format
Use this parameter to select between the 12-hour format and the
24-hour format.
Automatic Daylight Savings Time
When Automatic Daylight Savings Time is enabled (On), the
thermostat automatically switches to daylight savings time on the
second Sunday of March and reverts back to normal time on the first
Sunday of November.
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