Quarter phases advance through consecutive synodic cyclesLive current inputs
Date & Time
Moon Phase Date Schedule Calculator
Generate an approximate UTC schedule of new moon, first quarter, full moon, and last quarter events from a chosen start date, with cycle spacing and optional local fixed-offset labels.
First scheduled phase event—
Last scheduled phase event—
Scheduled event count—
Next modeled full moon—
Mean quarter-phase spacing—
Local-date rollovers—
First planning deadline—
Schedule coverage—
Lunar event schedule helix
Quarter phases advance through consecutive synodic cycles
Each cycle is a row on a helix-like calendar. Phase glyphs, planning-lead tails, and local-date rollover badges make the repeated schedule visually distinct from a flat list.
Phase event schedule
Approximate UTC and local fixed-offset phase events
Local labels use the entered fixed offset; the event window is a planning band, not an astronomical uncertainty statement.
| Phase | Estimated UTC | Local label | Planning deadline | Window start | Window end |
|---|
Schedule setup
Choose the horizon and event density
- Enter the first date that belongs in the schedule.
- Select enough cycles for the real planning horizon.
- Use a fixed offset only after resolving DST for each date.
- Set planning lead time from the work required before an event.
- Choose major-four or new/full output based on the use case.
Schedule construction
Event recurrence is phase-based, not calendar-month based
Lunar events do not recur on the same calendar day. The schedule advances by fractions of the mean synodic period, so dates move through the civil calendar.
Planning deadlines and windows are derived from each event rather than reused as decorative fields. The chart and table update when cycle count, phase set, offset, lead, or window changes.
Calculation method
Advance from the reference epoch in quarter-cycle increments
The first major phase on or after the start date is located from the epoch. Later events are spaced by one quarter of the mean synodic month, or one half-cycle when only new and full moon are selected.
Detailed calculation process and general formulas
q = P_syn / 4k_0 = ceil((T_start − T_epoch) / q)T_k = T_epoch + k × qT_local,k = T_k + zT_plan,k = T_k − L; window = T_k ± H/2Symbols, meanings, and units
- P_syn, q
- mean synodic month and mean quarter-cycle spacingdays
- k_0, k
- first and subsequent event indicesdimensionless
- T_k
- estimated UTC phase-event instantdate-time
- z, T_local,k
- fixed UTC offset and resulting local labelhours; date-time
- L, H
- planning lead and event-window widthdays; hours
Schedule operations
Turn approximate events into an actionable planning calendar
The schedule distinguishes the astronomical estimate, the local display label, and the date by which preparation should begin.
First event
—First selected phase on or after the start date.
Next full moon
—Nearest modeled full moon within the schedule.
Planning lead
—Earliest preparation deadline derived from the event.
Civil-date changes
—Events whose fixed-offset local date differs from UTC.
Decision takeaway: Export exact ephemeris times for execution; use this schedule to structure early planning and cadence.
Schedule review
Adjustments required before operational use
- High-precision ephemeris replacement
- Daylight-saving transitions by event date
- Local visibility and weather
- Site access or safety windows
- Resource and staffing deadlines
Schedule sources
References to attach to the final calendar
- Authoritative phase ephemeris
- IANA time-zone conversion
- Observation or event location
- Operational lead-time checklist
- Weather and visibility source
Practical applications
Decisions this calculator is designed to support
Four-cycle photography plan
A photographer schedules major phases and begins logistics three days before each event.
What the result clarifies: The helix shows event cadence while the table supplies preparation deadlines.
New/full community calendar
A planner filters to new and full moon only for a lower-density schedule.
What the result clarifies: The event count and spacing change instead of leaving empty quarter-phase placeholders.
Worked example
Current-input substitution and reconciliation
Model limitations
Times are mean-cycle estimates, not precision ephemeris results. Fixed offsets do not automatically adjust for daylight saving. Local visibility, moonrise, altitude, weather, terrain, and observational requirements are outside the model.
Moon Phase Date Schedule Calculator FAQ
Why are events not exactly seven days apart?
A quarter of the mean synodic month is about 7.38 days, not one civil week.
What does the event window represent?
It is a user-entered planning band around the estimated event, not a statement of astronomical uncertainty.
Does the local offset update for DST?
No. Enter the correct offset or use a time-zone database for each date.
Can I schedule only full moons?
The current filter offers major four or new/full; use an ephemeris for a custom phase list.