Possible Clues:

• Abbr. for a word also with abbrs. by its first two, or first four, or first five letters
• Almost time for TGIF
• Turkey Day: Abbr
• Day when the Last Supper is commemorated: Abbr
• Thanksgiving Day: Abbr
• Via, informally
• Day of Thanksgiving: Abbr
• Day to post a throwback picture on social media: Abbr
• Day following hump day: Abbr
• Part of MTWTF, briefly