Holy Day Calculations Summary.

Places to get the required data.

Go into www.timeanddate.com

Click on the menu item "Calendar", and print out the next years calendar. They give a number of options. I like the one on the LH side - squared box for a day.

Or you can print out a blank yearly form from "blank".

Then click on the menu item "Sun and Moon". Click on "Seasons", and put  "UTC" where it says "Place or country". Recalculate (do search) and print it out. This will give you the equinoxs.

To get the moon phases in UTC time, go to


I like this one as the UTC times are in 24 hour format.

Enter the year you want, put the month to January, and the date to 1st,  No. of phases to 50 (to cover the year), and then "get data". Print it out. Clicking on Data Services, you can also get the equinox (but the page might not print in full).

And alternative for the new moons is: https://www.calendar-12.com/moon_phases/2018

If you change the date at the end of the URL, it will go straight to it, if not at the bottom of the chart you can select a different date. The first section is in local time, but the second section has the UTC times and dates - this is what you want. A slight problem is that the UTC times are in 12 hour format (but only the first six hours are critical to the calculations, so it does make a lot of difference).

Now you have all the information you need.

Doing the calculations.

Choose either a printed out calendar to write on, or the blank form for the year. I slightly prefer the single page to start things off - but you do need a calendar to count off the days.


The first thing is to confirm the two equinox dates.

The equinox is a single point in time, but we still have to work out which day it falls on. This is different than for the new moons - for the new moons we need to find the day with a new moon in existence at the start of the day, but for the equinoxes we need the day that it happens. Look at the time. If the time is less than 6 hours UTC - then the event has already occurred for our calendar, as God's day starts at sunset, which is six hours before the world's day starting at midnight. So - if it is before 6:00 am - then we take the day before. If it is 6:00 am or later, we take the given day.

New moon.

Look at the date and time in UTC for each of the new moons. If the time is less than 6:00 hours, take the date and mark it on the calendar. If the time of day is 6:00 hours or greater, increase the date by one, and mark it on the calendar. This is the start of each month.

Fill in the details.

When all the new moons are done, look for the month starting after the March equinox (can't be the same day as the equinox). That is the first day of the new year for God's calendar.

Count down 14 days, and mark the evening before as the Last Supper. The 14th is the day the Passover lambs (and Christ) were killed. The 15th is the first Holy Day of Unleavened Bread. Seven days later (21st) is the Second Holy Day of Unleavened Bread.

Starting with the Sunday (the day after the Sabbath) during Unleavened Bread, count 50 days, and that Sunday is Pentecost. It is seven weeks plus one day.

The first day of the seventh month of God's calendar is Trumpets, followed by Atonement on the 10th, and Tabernacles starting on the 15th (a Holy Day), and Last Great Day on the 22nd. Trumpets will have a new moon in the previous 24 hours (the day starts with a new moon in existence) and Tabernacles has to start after the equinox.

Make a note at the top that the actual Feasts start the evening before at sunset. Now you have God's Holy Days marked on a calendar.

More details.

These instructions are just a summary.

To understand the Scriptures that back them up you will need to read,

The theory behind the calendar.

Calendar without charts.

Why the six hours?

Some may wonder why a new moon or an equinox occurring in the first six hours of UTC time in a day, are actually occurring before our Biblical day starts.

Hopefully the diagram below will help.

Sun/earth position at start of day.

The Biblical day starts when the sun sets at the International Date Line (IDL). For calculation purposes, this is taken as 6:00 pm (6:00 hours UTC). There is no problem in taking 6:00 UTC hours as a standard sunset time at the IDL, as at the NH Spring and Autumn equinox the sun will be setting near 6 :00 UTC. Pentecost is counted, so it is not affected by the new moon. This is standard practice for the Hebrew Calendar.  I have not found any accurate published sunset times for the IDL.

Once the first day of the year is correct,  the Holy Days will be in their correct "season".

The IDL is at 180 degrees longitude, and the times in UTC are calculated for a point at 0 degrees  - or half a day (12 hours) earlier.

Thus, if it is 6:00pm at the IDL (180 degrees), then it is 6:00am at the UTC marker (zero degrees longitude).

To convert a new moon time in UTC to local time at the IDL, we have to add  the 12 hours difference between UTC and the IDL, and then substract six hours because we start the day early at sunset and not midnight.

Thus, we end up with a six hour difference.

So - any new moon with a UTC time of less than 6:00 hours, has already happened by the time the IDL reaches 6:00pm. Since there is a new moon in existence at the start of our Biblical day, the date given by UTC time for the new moon, can be taken as the first day of the month.

Any new moon with a UTC time of 6:00am or greater will occur in the next 24 hours, so the following day is taken as the start of the new month.

Points to check.

When you have your new calendar worked out, a few key points to check out are:-

The earliest a new year can start is the day after the March equinox.

The Feast of Tabernacles has to start after the September equinox.

Pentecost has to be on a Sunday

Bob Orchard July 2014

While this information is made freely available (Mat 10:8b) , and can be printed out, it is done with the understanding that there will only be fair and honest use of the material, and that it will be copied in full with no alterations.