Can I sweep the grave on the first day tomorrow?

You can't. According to the information, grave-sweeping is not allowed on the first day of New Year's Day, and it is carried out on the first three days and the last four days in Tomb-Sweeping Day. Grave-sweeping is a "grave-sweeping sacrifice" and "respect for time thinking" to ancestors, and its custom has a long history. In the north, it is called going to the grave; in some places, it is called "sweeping mountains" or "worshipping mountains"; in the south, it is called "hanging mountains" or "hanging paper".