This is intended to be a complete implementation of strftime as specified in C17, although it lacks meaningful support for time zones or non-C locales.
This may be either 50 or 60, depending on the system's video frequency setting (50Hz PAL or 60Hz NTSC). The video setting can be determined by inspecting bit 4 of the LANGSEL soft switch, documented in Appendix E of the Apple IIGS Firmware Reference.