A radio signal controlled clock which decodes time information in a radio signal and thereby determines the current time. The clock collects and stores radio signal data as soon as a reasonably decodeable radio signal is located, even before the minute boundary of the radio signal's time base has been located. This data is stored and later used for decoding and verifying the digits of the time information after the minute boundary has been located. In another aspect of the present invention, an internal counter in the clock is periodically resynchronized with the radio signal, and the average of the adjustments required for this resynchronization is maintained. When no radio signal is available, or the radio signal is too noisy to be reliably decoded, the average internal counter adjustment value is used to periodically adjust the internal counter--and thereby helps to keep the clock's internal counter as closely synchronized with the radio signal's time bases as possible when the radio signal is not available or not usable.