A calendar mechanism of a timepiece includes a date indicator having a date wheel portion provided with a notched portion. An operation lever attached to the date indicator is pivotable between a pre-feed allowing position, where a tooth-shaped engaged portion thereof is inserted into the notched portion whereby excess feeding of the date indicator is possible, and a normal feed allowing position, where the tooth-shaped engaged portion retreats from the notched portion whereby normal feeding is possible. The date indicator is rotated by a day earlier than the normal feeding when set to the pre-feed allowing position. A driving lever structure includes a cam follower engaged with a month cam and is driven in response to rotation of the month cam to allow the operation lever to be pivoted between the normal feed allowing position and the pre-feed allowing position.