RegEx String Validator - regex

Question

In my MVC3 application, on one of the entities I am saving the Date of Birth as a string. Why ? because my application allows the storage of the date of birth of people long dead, eg. Socrates, Plato, Epicurus ... etc and as far as I know the DateTime class doesn't allow that.
Now obviously we don't know the exact date of birth of Epicurus for example, we just know the year of birth [ 341 BCE ], so what I am thinking of doing is building a custom validator, that will validate the input string for the Date of Birth and make sure that they all match the following format:
12 Feb 1809
Feb 1809
341
341 BCE
Oct 341 BCE
11 Mar 5 BCE
I need to write a regular expression that will match any of the above, and of course not match anything else.
Update
Thank you very much, I wish I was as good as you lot in building RegExes ! Since my application is with ASP.net MVC3, I would like to stick with the .NET RegEx class (for convenience's sake).
luastoned answer seems to work; I can't seem to break its logic with all the test data I've thrown at it.
One thing though, can I also allow BC? Because some people use BC and others use BCE < would that be possible? And, am I right that the regular expression can not replace BC with BCE? I have to do that manually through my C# code - the RegEx would just either match or not, is that correct?
Update 2
M42's Regular Expression seems to be working better. I've just copied it and used it in my Custom Validator (code in PasteBin link below).

Answer 1

How about :
/^(?:\d+\s)?(Jan|Feb|Mar|Apr|May|Jun|Jul|Aug|Sep|Oct|Nov|Dec)?(?:\s?\d+)(?:\sBCE)?$/
Here is a perl script with test cases:
#!/usr/local/bin/perl
use strict;
use warnings;
use Test::More;
my $re1 = qr/^(?:\d+\s)?(Jan|Feb|Mar|Apr|May|Jun|Jul|Aug|Sep|Oct|Nov|Dec)?(?:\s?\d+)(?:\sBCE)?$/;
while(<DATA>) {
chomp;
if (/$re1/) {
ok(1, "input = $_");
} else {
ok(0, "input = $_");
}
}
done_testing;
__DATA__
12 Feb 1809
Feb 1809
341
341 BCE
Oct 341 BCE
11 Mar 5 BCE
12D09
1s909
A3 43 4 BCE
a 1
3F9
abc
BCE
123b456
output:
# Looks like you failed 9 tests of 15.
ok 1 - input = 12 Feb 1809
ok 2 - input = Feb 1809
ok 3 - input = 341
ok 4 - input = 341 BCE
ok 5 - input = Oct 341 BCE
ok 6 - input = 11 Mar 5 BCE
not ok 7 - input = 12D09
not ok 8 - input = 1s909
not ok 9 - input = A3 43 4 BCE
not ok 10 - input = a 1
not ok 11 - input = 3F9
not ok 12 - input =
not ok 13 - input = abc
not ok 14 - input = BCE
not ok 15 - input = 123b456

Answer 2

this looks likes the weirdest Regex I've ever made:
(\d+\s?)?(Jan|Feb|Mar|Apr|May|Jun|Jul|Aug|Sep|Oct|Nov|Dec)?\s(\d+\s)?(BCE)?
I have no idea how many false positives would go through though..
You can check the sample on Regexr

Answer 3

Not quite a friend of RegExr (and not knowing the limitations of regexes in MVC3), allow me to present a PHP version with named captures (demo):
(?:(?:(?P<date>\d{1,2})\s)?(?P<month>Jan|Feb|Mar|Apr|May|Jun|Jul|Aug|Sep|Oct|Nov|Dec))?(?:(?:^|\s)(?P<year>\d+))?(?:\s(?P<bce>BCE))?
This is based on #luastoned's answer.