Thread: 3 digit year problem

Hi,

Is there any rhyme or reason to these ISO format date parsing rules?

test=# select '1-1-1'::date;
ERROR:  Bad date external representation '1-1-1'
test=# select '69-1-1'::date;   date
------------2069-01-01
(1 row)

test=# select '50-1-1'::date;   date
------------2050-01-01
(1 row)

test=# select '40-1-1'::date;   date
------------2040-01-01
(1 row)

test=# select '30-1-1'::date;
ERROR:  Bad date external representation '30-1-1'
test=# select '100-1-1'::date;
ERROR:  Bad date external representation '100-1-1'
test=# select '999-1-1'::date;
ERROR:  Bad date external representation '999-1-1'
test=# select '1000-1-1'::date;   date
------------1000-01-01
(1 row)

Why can't someone store the year without having to pad with zeros for years
between 100 and 999?

What's wrong with 30-1-1 and below?  Why does 40 work and not 30?

Chris

> Is there any rhyme or reason to these ISO format date parsing rules?

Yes. Though adjustments to the rules are possible, so things are not set
in concrete. There *should* be a complete description of the date/time
parsing rules in the User's Guide appendix.

> Why can't someone store the year without having to pad with zeros for years
> between 100 and 999?

To help distinguish between day numbers and years. We used to allow more
variations in the length of a year field, but have tightened it up a bit
over the years.

> What's wrong with 30-1-1 and below?  Why does 40 work and not 30?

Because "30" *could* be a day. "40" can only be something intended to be
a year. And input is not enforced to be strictly ISO-compliant, so
"30-1-1" *could* be interpreted multiple ways.
                     - Thomas