Rep. Nita Lowey (D-N.Y.) noted in her tweet that Clinton is her constituent. Clinton has a home in New York and represented the state in the Senate from 2001 to 2009. Sen. Kirsten GillibrandKirsten GillibrandOvernight Defense: Mattis cruises through confirmation hearing Mattis cruises through confirmation hearing Senate teeing up Mattis waiver MORE (D-N.Y.), who replaced Clinton in the Senate, also tweeted recognition of the birthday of her "mentor, role model and friend."

Sen. Mark UdallMark UdallLive coverage: Tillerson's hearing for State The rise and possible fall of the ‘Card’ in politics Gardner's chief of staff tapped for Senate GOP campaign director MORE (D-Colo.) and Rep. Emanuel Cleaver (D-Mo.) also sent birthday tweets. 

The former first lady turned 65 on Friday. She does not have a public Twitter account. 

The official State Department schedule has the whole day blocked off for Clinton to celebrate her birthday, and includes a note that it "doesn't get more closed press than this," meaning the media is not invited to cover any plans. Clinton will be back on a plane Monday for a three-day trip to Algeria, Bosnia and Herzegovina, Serbia, Kosovo, Albania and Croatia.

Updated at 6:09 p.m.