How lunar eclipse contacts and durations are calculated
Eclipse contacts mark modeled boundaries between shadow phases. Penumbral contacts bound passage through Earth's lighter outer shadow, umbral contacts bound the partial-or-greater phase, and totality contacts exist only when the Moon becomes fully immersed in the umbra.
The finder reports these global instants around a calculated peak. It does not infer contacts from a generic eclipse length, and it does not add totality rows to partial or penumbral events where that phase never occurs.
Peak and semi-duration define each pair
For every shadow phase supplied by the engine, the method has a semi-duration measured from peak. Subtracting that interval gives the begin contact; adding it gives the end contact. The full phase duration is twice the semi-duration. This symmetric construction keeps all contacts tied to the same modeled event rather than mixing independently rounded catalogue rows.
Contact order is validated: penumbral begin precedes umbral begin when an umbral phase exists, peak lies between corresponding begin and end instants, and the outer phase ends last. A total eclipse adds a narrower totality interval inside the umbral interval. A partial event has no totality contacts, while a penumbral event has neither umbral nor totality contacts.
Global timing is not local visibility
An eclipse peak is one physical instant worldwide, although its formatted clock time and civil date depend on the chosen display zone. The finder uses the input zone to resolve and present time, not to alter the event. It therefore does not need latitude or longitude for the global search.
A local observer may have the Moon below the horizon for some or all contacts. Clouds, daylight, terrain, and buildings add further constraints. Those questions require a separate observer analysis, so the contact table deliberately stops at global shadow geometry and does not label an event visible from a city or country.
Worked partial-eclipse example
From an input of 26 August 2026 at 12:00 UTC, the next event is the global partial lunar eclipse of 28 August:
- Penumbral phase
- 01:23:36–07:02:02 UTC, about 338 minutes
- Umbral phase
- 02:33:24–05:52:14 UTC, about 199 minutes
- Peak
- 04:12:49 UTC
- Totality
- not present for this partial event
Peak falls inside both available intervals, and the umbral phase is shorter than the penumbral phase. An absent totality value is meaningful classification logic, not missing content.
Calculation limits
- Displayed contact times are rounded for reading; validation tolerances, not decimal formatting, define the tested agreement.
- Global contacts do not prove local horizon visibility or observing conditions.
- The method reports the phases supplied by the model and never extrapolates a nonexistent totality interval.
Use the working calculator
Open the Lunar Eclipse Finder to calculate another exact instant with the same production logic. The calculator accepts the relevant input and keeps result state on its single canonical tool page.