It was in February, only 17 months into his reign, that the British court announced that the king had cancer and that he would pause all public engagements during treatment.
Charles had been admitted in January for surgery for an enlarged prostate and it was during that procedure that the cancer was discovered.
The king has partly continued to work behind the scenes, but is now resuming the official events. His first assignment will be a visit to a cancer treatment center on Tuesday.
In June he will come together with the Queen Camilla to host a state visit by Japanese Emperor Naruhito and Masako of Japan.