The expression "time, times and half a time" appears in the books Daniel and Revelation:
And I heard the man clothed in linen, who was on the waters of the river, when he held up his right and his left hand to Heaven, and swore by Him who lives forever that it shall be for a time, times, and a half. And when they have made an end of scattering the power of the holy people, all these things shall be finished (Daniel 12:7).
And two wings of a great eagle were given to the woman, so that she might fly into the wilderness, into her place, where she is nourished for a time and times and half a time, from the serpent's face (Revelation 12:14).
Revelation 12 reveals the exact number of days for this period:
And the woman fled into the wilderness, where she had a place prepared by God, so that they might nourish her there a 1260 days (Revelation 12:6).
So the expression "time, times and half a time" means 1260 days. If 3½ times are 1260 days, than one time is 1260 : 3½ = 360 days.