A method and arrangement are provided for time synchronization between two geographically separated stationary clocks, such as first and second clocks located respectively at first and second ends of an AC power line. A first representation of an oscillating power line quantity is produced by measuring or recording the power line quantity at the first end of the power line, and time-stamping the first representation by the first clock. A second representation of the same oscillating power line quantity is produced by measuring the power line quantity at the second end of the power line, and time-stamping the second representation by the second clock. The first and second representations are compared to determine a clock offset between the first and second clocks. Based on the comparison, one or both of the first and second clocks are adjusted to reduce the determined clock offset.