A Kshaya Tithi is a "lost" or "skipped" lunar day — one that does not span a single sunrise at all. Since a tithi typically lasts 19–26 hours (close to, but not always longer than, the ~24-hour gap between sunrises), it's possible for a tithi to begin after one sunrise and end before the next sunrise occurs.

When this happens, that tithi has no sunrise to "rule" it. Per traditional Panchang rules, it doesn't get its own civil calendar day — it is considered kshaya (decayed/lost), and the calendar attaches it to the day governed by the preceding sunrise instead.

This calculator flags results as Kshaya whenever an Amavasya date was determined by this rarer fallback rule rather than a direct sunrise-within-tithi match, so you can verify unusual dates against your own tradition's conventions.