Short answer
Many families hold Mundan (the first haircut) in an odd-numbered year, such as the first or third, and ear piercing (Karnavedha) in infancy or early childhood, though customs vary. Choose a day when your child is well, check it in Find Good Times, and keep the ceremony outside Rahu Kalam. Comfort and hygiene come before any date.
How ChiChakra reads this
ChiChakra reads these as daily-timing questions: the Panchangam for your town, the Rahu Kalam slot, and your child's Chandrashtama days if you know their Moon sign. The age and month come from your family's tradition, which varies by region.
Getting the day right
Ask the barber or piercer about hygiene and aftercare, and pick a day when your child is rested and healthy.
Shortlist two or three dates, check them in Find Good Times, and drop any on the child's Chandrashtama days.
Some families hold Mundan at a temple on a festival day; the festivals page gives those dates for your city.
Good to know
If your child is unwell, postpone. A doctor's advice comes before any calendar.