Times past midnight can also be counted past the 24 hour mark, usually when the associated activity spans across midnight.
For example, bars or clubs may advertise as being open until "30時" (i.e. 6 am).
This is partly to avoid any ambiguity (6 am versus 6 pm), partly because the closing time is considered part of the previous business day,
and perhaps also due to cultural perceptions that the hours of darkness are counted as part of the previous day, rather than dividing the night between one day and the next.
Television stations will also frequently use this notation in their late-night scheduling. This 30-hour clock form is rarely used in conversation.