The "Download Now" link directs you to the iTunes App Store, where you must continue the download process. You must have iTunes installed in order to open the link, and you must have an active iTunes account to download the application. This download may not be available in some countries.
From Jason Stelzel:
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.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".