Developer Utilities
Small developer utilities that save a trip to a random website. Encode and decode Base64, explain a regex, build UTM links, generate QR codes and vCards, and more — the everyday helpers. Free in your browser, and available by API when you need them in a script.
Developer Utilities
J2 nodal precession rate calculator for satellite orbits
POST /astro/nodal-regression-rate$0.002Developer Utilities
Relativistic perihelion precession calculator
GR arcsec per orbit
POST /astro/relativistic-perihelion-shift$0.002Developer Utilities
Exoplanet transit duration calculator
central transit hours from P, R★, a
POST /astro/transit-duration$0.002Developer Utilities
Subtract weeks from a date
exact date calculator
POST /date/subtract-weeks$0.002Developer Utilities
Orbit total energy calculator
mass, mu, and semi-major axis
POST /astro/orbital-energy-total$0.002Developer Utilities
Add decades to a date
ISO ± N ten-year decades, free
POST /date/add-decades$0.002Developer Utilities
Add hours to a datetime
ISO clock shift in UTC, free
POST /date/add-hours$0.002Developer Utilities
Difference in decades between dates
whole decade calculator
POST /date/diff-in-decades$0.002Developer Utilities
Difference in minutes between two datetimes
signed UTC, free
POST /date/diff-in-minutes$0.002Developer Utilities
Subtract minutes from a datetime
UTC calculator
POST /date/subtract-minutes$0.002Developer Utilities
Days remaining in the quarter
calendar day counter
POST /date/days-remaining-quarter$0.002Developer Utilities
Midpoint between two dates
exact halfway datetime in UTC, free
POST /date/midpoint-between-dates$0.002Developer Utilities
Nearest weekday to a date
snap weekends to Mon–Fri business day, free
POST /date/nearest-weekday$0.002Developer Utilities
Net working days between dates
weekends and holidays excluded
POST /date/net-workdays-between$0.002Developer Utilities
Working days in a year
exclude weekends and holidays
POST /date/workdays-in-year$0.002Developer Utilities
Business days until a date
exclude weekends and holidays
POST /date/business-days-until-date$0.002Developer Utilities
Start and end of century
first and last year from an ISO date, free
POST /date/century-start-end$0.002Developer Utilities
Fraction of quarter elapsed
ISO datetime to 0–1 quarter progress
POST /date/fraction-of-quarter-elapsed$0.002Developer Utilities
Start and end of ISO week
Monday and Sunday dates from any day, free
POST /date/iso-week-start-end$0.002Developer Utilities
Start of next year
get January 1 from an ISO date
POST /date/start-of-next-year$0.002Developer Utilities
Weeks until a future date
exact whole and fractional weeks
POST /date/weeks-until-date$0.002Developer Utilities
Ascension Day date calculator
39 days after Easter
POST /date/ascension-day$0.002Developer Utilities
Count a specific weekday in a year from an ISO date
POST /date/count-weekday-in-year$0.002Developer Utilities
Day number within quarter
one-based day of Q1–Q4 from ISO date
POST /date/day-number-in-quarter$0.002Developer Utilities
Convert .NET ticks to an ISO date and time
POST /date/dotnet-ticks-to-date$0.002Developer Utilities
Gregorian epact calculator
moon age on January 1, free
POST /date/epact-gregorian$0.002Developer Utilities
Excel serial number to date
1900 system converter with leap bug, free
POST /date/excel-serial-to-date$0.002Developer Utilities
Floor datetime to a minute or second interval in UTC
POST /date/floor-to-interval$0.002Developer Utilities
Gregorian to Ethiopian date converter
free calendar tool
POST /date/gregorian-to-ethiopian$0.002Developer Utilities
Gregorian to Hebrew date converter
deterministic calendar arithmetic
POST /date/gregorian-to-hebrew$0.002Developer Utilities
Gregorian to Hijri date converter
tabular Islamic calendar, free
POST /date/gregorian-to-hijri$0.002Developer Utilities
Gregorian to Julian calendar date converter
POST /date/gregorian-to-julian-cal$0.002Developer Utilities
Gregorian to Indian Saka calendar converter
free ISO date tool
POST /date/gregorian-to-saka$0.002Developer Utilities
Hijri year length calculator
354 or 355 days
POST /date/hijri-year-length$0.002Developer Utilities
Is a weekend day?
Saturday/Sunday checker for an ISO date
POST /date/is-weekend$0.002Developer Utilities
Japanese nengo era year calculator
Reiwa, Heisei, Showa from ISO date
POST /date/japanese-nengo-year$0.002Developer Utilities
List all of a weekday in a month
every Monday–Sunday date, free
POST /date/list-weekday-dates-month$0.002Developer Utilities
Maya Calendar Round Calculator for Any Date
POST /date/maya-calendar-round$0.002Developer Utilities
Maya Long Count from date
free converter
POST /date/maya-long-count$0.002Developer Utilities
Minguo ROC to Gregorian date converter
POST /date/minguo-to-gregorian$0.002Developer Utilities
Modified Julian Day to date converter
Gregorian UTC
POST /date/mjd-to-date$0.002Developer Utilities
Persian Jalali to Gregorian date converter
POST /date/persian-to-gregorian$0.002Developer Utilities
Shrove Tuesday date
calculate Mardi Gras for any year
POST /date/shrove-tuesday$0.002Developer Utilities
Truncate datetime to unit
year, month, day, hour, minute in UTC
POST /date/truncate-to-unit$0.002Developer Utilities
Week number with custom first day
any weekday start, free
POST /date/week-number-custom-start$0.002Developer Utilities
Weekday of New Year's Day
January 1 calculator
POST /date/weekday-of-new-year$0.002Developer Utilities
Black Friday date calculator by year
POST /date/black-friday$0.002Developer Utilities
Easter Monday date
Gregorian Easter Sunday plus one day by year
POST /date/easter-monday$0.002Developer Utilities
Tabular Eid al-Adha date
Hijri to Gregorian calculator
POST /date/eid-al-adha-tabular$0.002Developer Utilities
US Father's Day date
third Sunday of June calculator
POST /date/fathers-day-us$0.002Developer Utilities
Groundhog Day date and weekday calculator by year
POST /date/groundhog-day$0.002Developer Utilities
Memorial Day date calculator
last Monday of May, free
POST /date/memorial-day$0.002Developer Utilities
Palm Sunday date
Sunday before Gregorian Easter for any year
POST /date/palm-sunday$0.002Developer Utilities
Approximate Autumnal Equinox Date and Time Calculator
POST /date/autumnal-equinox-approx$0.002Developer Utilities
EU daylight saving start date
last Sunday of March, free
POST /date/daylight-saving-start-eu$0.002Developer Utilities
Approximate Holi date calculator
lunar full moon rule
POST /date/holi-approx$0.002Developer Utilities
Meteorological season of a date
fixed months by hemisphere
POST /date/meteorological-season$0.002Developer Utilities
Passover Start Date Calculator by Year
POST /date/passover-start$0.002Developer Utilities
Rosh Hashanah date calculator
Gregorian from Hebrew calendar
POST /date/rosh-hashanah$0.002Developer Utilities
UK summer bank holiday date
last Monday of August, free
POST /date/uk-summer-bank-holiday$0.002