This circuit is from General Electric from the 80s, using a relay with high current contacts (20 A). The transistor admits equivalent, and any phototransistor can be used as a sensor.
We found this circuit in the October 1992 Radio Electronics magazine. The frequency is given by C1...
This conventional LED flasher circuit has a configurable multivibrator configuration with PNP...
This extremely slow circuit produces one pulse per month and can be used in a timer. We found it...