@DOWI — returns the day of the week of the specified date as a number, 1 for Sunday through 7 for Saturday. The date may be in any input date format supported by this plugin, and it must be a valid date within the supported range.

Syntax:
%@DOWI[date,infmt]

datethe date to examine; defaults to today’s date if omitted
infmtthe input date format, used to interpret ambiguous dates