Tzolkin is the repeating patterns of time (cycle) of 13 tones x 20 day signs x 9 night lords. The best way to show this pattern is by creating a model you can see visually.
Examine the wheel on the right, it has 20 day signs in the outer ring, 13 tone symbols inside the day sign ring and 9 night lord ring inside the tones ring.
Each day the wheels turn one day sign position, the inner rings will follow and move one positions relative to the outer day sign wheel.
Turning the wheel clockwise advances by one day, anti-clockwise retards by one day. Give it a try rotate the day sign wheel and watch the inner rings follow.
The initial wheel position is worked out using the Goodman-Martinez-Thompson, or GMT, correlation.
The Tzolkin does not skip days, try it rotate the wheel and watch the days progress. This is the key difference between the true Maya (Tzolkin) calendar, it does not skip days.
You may have come across another calendar called Dreamspell which claims to be Maya (Tzolkin) calendar, that calendar skips days and is not in sync with the true count Maya (Tzolkin) calendar. The symbols and names on the Dreamspell may look the same but at the end of the day their days do not line up with the true Mayan (Tzolkin) calendar.