According to the man page, chage should understand dates in the format YYYY-MM-DD.
This does not appear to work. Instead, chage interprets YYYY-MM-DD to mean YYYY days since the epoch.
MM and DD are ignored. However, YYYY/MM/DD works fine. I have observed this only on the S/390 platform,
but the source only looks for a date if it has a "/" in it.
You could (a) fix chage to look for dates with hyphens
or (b) fix the man page to say YYYY/MM/DD.
Fixed in 20000826-2.