FROM TO syntax explained

I am a bit confused about the time frame commands FROM and TO and what they
mean.  I want to run my statistics on a monthly basis and I want to run it
first thing at the beginning of every month.

I want full statistics from the previous month, so I want to say "Run
statistices from the beginning of the previous month to the end of the
previous month"

The example in README is similar to what I need, but I am confused about a
few things:
FROM yyMMdd 

FROM -01-00+01   # from tomorrow last year
TO -00-0131  # to the end of last month (OK even if last month
             # didn't have 31 days)


FROM  -01-00+01
Yy
-01 = Last Year
MM
-00 = ??  (What is a minus 00 month..?)
dd
+01 = Tomorrow


TO -00-0131  
YY
-00 = ??  (What is a minus 00 year?)
MM
-01 = Last month
Dd
31 = The 31st or last day of the month

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