The term POSTMARK PARTS can be broken down into two crossword solutions: DATES (5 letters). Postmarks are typically used on mail to indicate the date and time of when the item was sent. The date part of a postmark is usually printed in the form of a stamp, which is why it is referred to as a 'date stamp'. This stamp is usually placed on the envelope or package before it is sent. The date stamp is an important part of the postmark, as it helps to identify when the item was sent.