An "Adhik Maas" is an extra month in the Hindu calendar. What is the month after this month? There are texts on it but people have different opinion. I am confused.
A Luni-solar year is 354 days consisting of 360 thitis. Depending on the location of sun and moon with respect to the nakshatras we will end up with a situation like a adhik maas. Adhik maas is basically two full moons in the same group of nakshatras which constitute a month. Chaitraa maasa is when full moon happens in either Chitra or Swati nakshtra. If two consecutive full moons happen in Chitra and then Swati nakshatra both the months will be called Chaitra. The next month after Chaitra will be Vaishaaka Maas. We can also land up with a situation of a full moon missing both the nakshatras in a group. Then this is a kshaya or non existent maas. Practically the calculation of moon's motion is the most complex among all grahas.