A background for the calendar story -- Time cycles and the heavenly bodies -- The time cycle of life -- Features of the ancient calendars -- A calendar for Egypt -- The moonlight calendar -- The calendar of the seven-day week -- Time ideas from the Euphrates Valley -- Today's calendar; its background and modifications -- Julius Caesar's calendar for the Roman World -- The enlargement of the Roman calendar under Constantine -- The calendar correction of Gregory -- The place of Easter and Christmas in the calendar -- The present calendar; and a possible one for the future -- Backward extension of the calendar plan: methods, old and new, for dating the events of early history -- Solving by astronomy the riddle of some early dates -- Using carbon, the chemical element, as a reverse-acting clock of time -- Exploring history with tree-ring records -- Nature's seasons and the calendar; a concluding section -- Spring and springtime a personal postlude.