According to Accounting Coach, post-dated checks are not considered legal currency and should not be entered until the date of the check. Entering the check before its date artificially inflates the company's cash account.
For example, if a check for $250 is received on the 11th of the month, but is dated for the 16th, entering it on the 11th results in a false cash balance until the 16th, because the check is not a valid form of currency.
On the 16th the cash account is debited for $250 to reflect the increase in cash from the check. The accounts receivable account is credited for $250 to decrease its balance.