Bigday

4 clues
Much-anticipated time
One's marriage or graduation
It may be circled on a calendar
Exciting thing circled on a calendar
Similar answers:
Abbaniceday
Abcdaytimehosts
Abig
Abigail
Abigailadams
Abigaildeanwill
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Abigailvanburen
Abigailwilliams
Abigbangmay
Abigdealoutofit
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Abigturnoff
Abnerdoubleday
Abnersingleday
Actbig
Actedbig
Actedthebigcheese
Aday
Adayago