SMPTEcalc offers an easy way to calculate SMPTE timecode durations, in and out-points as well as conversions to other formats. It supports 23.976 (a.k.a. "23.98"), 24, 25, 29.97 DF and 30 ND frames per second framerates along with 4 time/counter display formats: timecode, realtime, seconds and frames. You can freely switch between various formats and timebases and do simple IN/OUT/DURATION math to answer questions or diagnose problems related to timecode.
You can also also enable "Accumulate and FIT" mode (whenever a plus or minus symbol is showing) that accumulates a total of multiple DURations in the OUT point. This OUT point can easily be OFFSET by changing the IN point to see how it would fit in an editing timeline or other context that has a hole to be filled.
Diagnose a "drop-frame" vs. "non-drop-frame" issue by entering a timecode in one timebase (29.97 DF) and then switching to another (30 ND).
Calculate the frames of animation needed by entering a duration in "Seconds" and then switching the display to "Frames".
Please take a moment to visit SMPTEcalc's sponsors who help to keep SMPTEcalc a free app!