The date inside the mail (on the "Date:" header) was for February.
Since spam is junk there is no reason to expect this date to be valid, spammers frequently use future or past dates to end up at the top or the bottom of the in tray and thus more prominent and more likely to be read. Sometimes it is simply because the date is set wrong on the computer sending the email. SpamAssassin uses dates in future and distant past as an indication of likelihood that an email is spam. It is spam - hit delete and move on - unless you need a better spam filter. Simon