Honeywell RTH7500 Guide D'installation page 19

System setup About your new thermostat
Year setting (first two digits)
Function
Press
0120
Options: 20 = Year 20xx
21 = Year 21xx
Year setting (second two digits)
Function
Press
0130
Options: 01 -
Month setting
Function
Press
0140
Options: 01 -
Date setting
Function
Press
0150
Options: 01 -
to change the first two digits of the year:
s/t
to change the last two digits of the year:
s/t
99 (i.e., 2001 - 2099)
to change the current month:
s/t
12 (i.e., January - December)
to change the current date:
s/t
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RTH7400/RTH7500