A clock signal for use by a circuit can be switched between clocks glitchlessly. A series of delay devices are connected in series based on an integral timing ratio. The integral timing ratio can be based on a ratio of the one of the clock's frequency or period to the other's frequency or period. When a clock select signal is received, the select signal is qualified and then delayed an amount of time based on the integral timing ratio, using the delay devices. The number of delay devices in each series can be the next largest integer to the integral timing ratio, plus one. The clock signal can then be glitchlessly switched from one clock to the other.