I know from locally stored knowledge that:

-7 hours
is the time zone differential of
Mountain Standard Time
([fact: ["20030748@trueknowledge.com"]])

-4 hours
is the time zone differential of
Eastern Daylight Time
([fact: ["20030737@trueknowledge.com"]])

By calculation (generator: ["first_parameter@trueknowledge.com"]) I know that:

-7 hours and 0 minutes
is the first parameter of
-7 hours

-4 hours and 0 minutes
is the first parameter of
-4 hours

By calculation (generator: ["strictequal1@trueknowledge.com"]) I know that:

January 1st 1, 01:01:01
is strictly equal to
January 1st 1, 01:01:01

-7 hours and 0 minutes
is strictly equal to
-7 hours and 0 minutes

-4 hours and 0 minutes
is strictly equal to
-4 hours and 0 minutes

By calculation (generator: ["timepoint_sum@trueknowledge.com"]) I know that:

December 31st 0 BC, 18:01:01
is the timepoint sum of
January 1st 1, 01:01:01 and -7 hours and 0 minutes

December 31st 0 BC, 21:01:01
is the timepoint sum of
January 1st 1, 01:01:01 and -4 hours and 0 minutes

By calculation (generator: ["timepoint_difference@trueknowledge.com"]) I know that:

-3 hours, 0 minutes and 0 seconds
is the length of time between the timepoints
December 31st 0 BC, 21:01:01 and December 31st 0 BC, 18:01:01

By calculation (generator: ["difference_between_lengths_of_time@trueknowledge.com"]) I know that:

-3 hours, 0 minutes and 0 seconds
is the difference between the scalar quantities
-7 hours and 0 minutes and -4 hours and 0 minutes