Do you burn incense and set off firecrackers for your ancestors on the fifteenth day of the first lunar month?

In fact, you can burn incense anytime and anywhere. What matters is not time, but a person's respect and piety, which means "sincerity is the spirit"

As for the fifteenth day of the first month, it is because incense not only supports buddhas and bodhisattvas, but also supports six other sentient beings. Among them, there is a supernatural creature who eats incense and incense also supports them. A day of supernatural beings is equivalent to a month on earth, and the incense on the first and fifteenth days is equivalent to their lunch and dinner, so it is more meaningful to burn incense at this time.

As for your ancestors, if they are not practitioners, they must be in the six divisions of the wheel of karma. Incense them will be of great benefit. If you can recite Tibetan scriptures for them one to seven times, your merits will be even greater!