Radio Shack TRS-80 Model II Reference Manual page 158

Modell! TRSDOS
In general to find a new date from a date and a timespan, the date and
timespan should be entered like this:
mm
1ddlyyyytJjjjjj
where mm is a two-digit number 01-12;
dd,
a two-digit number 01~31;
yyyy,
a four-digit number 1600-9999; andjjjjj (Julian measure oftime), a
five-digit number 00001-65535. (Julian time refers to the measure of time
in days rather than hours, years, months, etc.) Be sure to use leading
zeroes as required to make up the specified number of digits. And don't
omit the space
OS)
between
yyyy
and jjjjj.
Date Difference
To find the number of days between two days, type D in
response to the initial prompt (A/D). In response to the
ENTER
PARAMETERS
prompt, type in your data as in this sample:
104/15/197912/31/1979
The program will print the number of days between the dates you entered:
625.
In general to find a timespan between two dates, the dates should be entered
like this:
mmlddlyyyy'flfmmlddlyyyy
where mm is a two-digit numberOl-12, dd, a two-digit numberOl-31; and
yyyy, a four-digit number 1600-9999. The earlier date must come first.
Since the maximum timespan that can be returned is 65535 days, the two
dates must not be separated by more than 179 years. Use leading zeroes
where necessary to make up the specified number of digits, and don't omit
the space
(.~)
between the two dates.
194