Calculating the day of the lunar cycle...

[AndyWB]

Okay, I figure this should be easy, but when I try Googling I get endless articles about figuring out when Easter is, or the Chinese calendar, or various other religious reasons.

I've a spreadsheet with all my observations in it. Each row has a date. I'd like to be able to resolve that date, roughly, to the day in the lunar month.

e.g. 21/02/2015 > 7

It's only rough, so I'm hoping things like it's elliptical orbit, etc., can be ignored.

Has anyone come across a simple formula for something like that?

[Floater]

Try moongiant.com. Might be what you're looking for, or help.

[Pondus]

Do you mean something like this   :

The formulas are in Norwegian so you have to change :

REST with  MOD     ( I think..)

HVIS  with IF          ( leaves empty cell if date not entered, if not you will end up with 29 in every cell)

Lunar day coloumn  has to be formatted as number, no decimals)

Copy and paste from c6 and down...

PS I have no idea wether u use ";" or "," in UK (within the formulas)

PS2 : Havent checked it for bugs or errors....

[cotterless45]

Personally I look in the diary. This may help. Sunday after the full Moon is why it's different every year ,

http://www.timeanddate.com/calendar/determining-easter-date.html

Old Nick.

[Steve Ward]

This'll be the one you want I think .... http://www.timeanddate.com/moon/uk/london

[Pondus]

Of course you have "phases of the moon" app for android, and numerous other possibilities, but I was

under the impression that you wanted lunar days implemented in a spreadsheet => enter date, and lunar day calculates automatic.

Rune

[AndyWB]

Yep, that's exactly what I was after, Pondus, and it seems to work. I wondered if there was a correlation between the point in the lunar cycle, and when I'd go out observing. It seemed I should be able to calculate that!