Unbelievable but true ... A date field in Drupal can not contain a date from before 1/1/1900. Not easy to discuss the Middle Ages ..
The forums are handling this issue (see link). You can install the patch, but the proposed workaround, is very useful.
Normally, you can enter an earlier date without problem if you have a node that still has not been saved . Good news for Feeds for importing a date.
If you after saving, want to change the date to an earlier date than is already stored and before 1/1/1900 of course, you get an error.
I had initially set that the person was born on 01/01/1780.
When I edit the node I get this to an earlier date.....
The workaround exists to click on the X mark and delete the date. Thereafter, save the node without storing the date and then reopen it to set the new date. Magic happens. Now one can add the date.
Yep. It seems that Drupal shifts to lower dates only with an empty date field.