Delimiter must not be alphanumeric or backslash

I just started getting the same error too. Changing priority to critical.

I also have:

warning: Missing argument 2 for date_formatter_process(), called in /sites/all/modules/date/date/date.theme on line 41 and defined in /sites/all/modules/date/date/date.module on line 115.

and

warning: Missing argument 3 for date_formatter_process(), called in /sites/all/modules/date/date/date.theme on line 41 and defined in /sites/all/modules/date/date/date.module on line 115.

These seem to be appearing on any node that has date fields in it. My date browser page which only lists two nodes at the moment has 15 of the above-type errors.

I changed line 1234 from:

$regex[] = array('([OZPe])');

to:

$regex[] = '([OZPe])';

and it got rid of the preg-replace errors for me. My content was showing up fine when the errors were present, and they still show up fine. I really don't know if this change will resolve any problems other people are having, I just know that my errors are gone and everything is still working.

Without this, the date_popup function on a calendar doesn’t work.

This patch is the same as Jeff’s comments; I’ve confirmed that it fixes the bug, so I'm marking RTBC.

@anthonym, see #263377: Missing argument 2 for date_formatter_process for the other 2 errors you mention.

I can also confirm that the patch fixes this issue. Thanks to those who sorted this!

Fix committed. It was right in the D6 version, got screwed up in the D5 version for some reason. Thanks!