Another word for this type of variable is modular.
In mathematics, modular arithmetic is a system of arithmetic for
integers, where numbers "wrap around" upon reaching a certain
value—the modulus. The modern approach to modular arithmetic was
developed by Carl Friedrich Gauss in his book Disquisitiones
Arithmeticae, published in 1801.
A familiar use of modular arithmetic is in the 12-hour clock, in which
the day is divided into two 12-hour periods. If the time is 7:00 now,
then 8 hours later it will be 3:00. Usual addition would suggest that
the later time should be 7+8=15, but this is not the answer because
clock time "wraps around" every 12 hours; in 12-hour time, there is no
"15 o'clock". Likewise, if the clock starts at 12:00 (noon) and 21
hours elapse, then the time will be 9:00 the next day, rather than
33:00. Because the hour number starts over after it reaches 12, this
is arithmetic modulo 12. According to the definition below, 12 is
congruent not only to 12 itself, but also to 0, so the time called
"12:00" could also be called "0:00", since 12 is congruent to 0 modulo
You can also refer, as suggested, to a "modular variable."