Moon Phase Calculator

From your date of birth, get exact age, Chinese nominal age (虛歲), days lived and days to next birthday.

Enter any two dates to get the calendar gap, working days, weekend days, plus year/month/day breakdown and total weeks/months.

Pick your local and target cities to convert a given clock time across time zones.

Add or subtract years, months, weeks and days from a start date to get the resulting date and weekday.

Count the working days between two dates (excluding weekends) — or add N business days to a start date to find the deadline.

Estimate the due date from your last menstrual period (LMP) using Naegele's rule, plus current gestational week, trimester and key pregnancy milestones.

Enter clock-in/clock-out times and break minutes to get total hours worked and gross pay — overnight (graveyard) shifts handled automatically.

Pick any date to see which day of the year (1–366), ISO 8601 week number, weekday, and how many days from the start and end of the year.

Enter any Gregorian date (past or future) to instantly find the day of the week — useful for birthdays, anniversaries and historical events.

Convert a Unix timestamp (seconds or milliseconds since 1970-01-01 UTC) to UTC, Hong Kong time and RFC 1123 HTTP date — and back. Built for debugging log files, API responses and database fields.

Pick a year and the Computus algorithm returns Easter Sunday plus Ash Wednesday, Palm Sunday and Good Friday.

Find your Chinese zodiac animal, stem-branch element, zodiac year and lunar (nominal) age from any birth date.

Enter your birth date to see your Western zodiac sign (Aries, Taurus, Gemini…) along with its element, modality and opposing sign.

Pick a birth month to instantly see the modern and traditional birthstones, the birth flower, the spanning zodiac signs and a colour swatch — handy when choosing jewellery or birthday gifts.

Convert a Gregorian calendar date to its Julian Day Number (JDN) and Modified Julian Day (MJD) — used in astronomy, history, and cross-calendar date math.

Enter any date and compute its ISO 8601 week number, ISO year and weekday — using the Monday-first / first-week-contains-Jan-4 rule.

Enter two clock times (HH:MM[:SS]) and instantly see the difference in hours, minutes and seconds — with overnight-shift handling and decimal-hour output.

Enter years of service and see the statutory paid annual leave entitlement under the HK Employment Ordinance §41AA.

Enter your date of birth to see when your next half-birthday falls, how many days away it is, and your current half-age (e.g. 33.5 years).

Enter a latitude, longitude and date to get the local sunrise, sunset, solar noon and total daylight hours using the NOAA solar position formula.