When I checked tyija1995's suggestion (using a value in A1 of +08'30) it returned a text string, which is confirmed by applying an ISNUMBER formula to the result, which returns FALSE.
Similarly ISTEXT on the result returns TRUE.
Having said that, if I apply a mathematical formula to the result, such as adding 1/24 to increase the time by another hour, Excel seems to recognise that this text string is actually a time value, and returns 01:08:30.