Below are the one letter variables available in any value expression.
For the register and print commands, these variables relate to
individual postings, and sometimes the account affected by a
posting.  For the balance command, these variables relate to
accounts---often with a subtle difference in meaning.  The use of each
variable for both is specified.

@table @code
@item t
This maps to whatever the user specified with @option{-t}.  In a
register report, @option{-t} changes the value column; in a balance
report, it has no meaning by default.  If @option{-t} was not
specified, the current report style's value expression is used.

@item T
This maps to whatever the user specified with @option{-T}.  In a
register report, @option{-T} changes the totals column; in a balance
report, this is the value given for each account.  If @option{-T} was
not specified, the current report style's value expression is used.

@item m
This is always the present moment/date.
@end table