A delay circuit used in a schedule controller includes a voltage detection unit, a timer, and a first electronic switch. The voltage detection unit receives an input voltage and compares the input voltage with a predetermined voltage. The timer is controlled by the voltage detection unit to calculate duration of an interval time. The first electronic switch is switched on or off under the control of the timer. When the input voltage substantially equals or exceeds the predetermined voltage, the timer calculates duration of the interval time, the timer generates and transmits a switch signal to the first electronic switch when the timing is reached, and the first electronic switch is switched on by the switch signal and provides an output voltage.