Why? Because it would be VERY easy for a nefarious person to alter the date and potentially cost you money.
"Say you agreed to make payments beginning on 1/15/20. The bad guy could theoretically establish that you began owing your obligation on 1/15/2019, and try to collect additional $$$," Rheingold wrote.
In the future, post-dating could be a problem too. For example, a check dated "1/1/20" could become "1/1/2021" next year, possibly making the uncashed check active again, Rheingold wrote. A similar method could be used for debts that are past the statute of limits.
The solution is easy: There's no harm in writing the full date. Writing the month out can also help.
https://www.usatoday.com/story/news/nat ... 795857001/