The rules that use the category "<offset_op>" are:

<time_point_name>

<h_hour> <offset_op> <up_to_two_digits>

<h_hour> <offset_op> <up_to_two_digits-pl> <time_interval_unit-minute-pl>

<h_hour> <offset_op> <up_to_two_digits-sing> <time_interval_unit-minute-sing>