How to convert this double prayer time to regular time?
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# Thread: How to convert this double prayer time to regular time?

1. Member
Join Date
Jan 2008
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98

## How to convert this double prayer time to regular time?

So forgive me for another post!
I just wanna calculate the prayer time in middle east country!
I can get the latitude and longitude data, and compute sunrise and sunset time.

I find a site http://www.tanzil.info/praytime/doc/calculation/
which give direction to compute prayer time!
But I have some questions about the formula given in the webpage!

Firstly, I am not sure in this formula, Does it take east longitude as negative, west longitude as positive?
(Because in the formula of computing sunrise and sunset, It takes east longitude as negative, west longitude as positive. North latitude as positive, South latitude as negative)

Secondly, It seems the results computed by the formula are doubles, which are not as
regular time, How can I convert them to regular time?

2. Elite Member
Join Date
Feb 2005
Posts
2,160

## Re: How to convert this double prayer time to regular time?

Originally Posted by fantasy1215
So forgive me for another post!
I just wanna calculate the prayer time in middle east country!
I can get the latitude and longitude data, and compute sunrise and sunset time.

I find a site http://www.tanzil.info/praytime/doc/calculation/
which give direction to compute prayer time!
But I have some questions about the formula given in the webpage!
Which formula? There are several on that page.
Firstly, I am not sure in this formula, Does it take east longitude as negative, west longitude as positive?
(Because in the formula of computing sunrise and sunset, It takes east longitude as negative, west longitude as positive. North latitude as positive, South latitude as negative)
That is typical for Lat/Lon coordinates
Secondly, It seems the results computed by the formula are doubles, which are not as
regular time, How can I convert them to regular time?
From looking at the site, it's probably returning Julian dates. You may need to read up on how to convert to some other format:

http://en.wikipedia.org/wiki/Julian_date

3. Member
Join Date
Jan 2008
Posts
98

## Re: How to convert this double prayer time to regular time?

I substitute my latitude 22 North, longitude -113(113 East), timezone +8 into these formulas,
but the prayer time I get seems not Julian time at all. Now I'll post my in face computation,
Please point out the places where's wrong!

d = jd - 2451545.0; // jd is the given Julian date, the Julian date of 2010/03/10 is 2455265.5000
d = 2455265.5000 - 2451545.0 = 3720.5

g = 357.529 + 0.98560028* d;
g = 357.529 + 0.98560028* 3720.5 = 4024.9476418

q = 280.459 + 0.98564736* d;
q = 280.459 + 0.98564736* 3720.5 = 3948.05282656

L = q + 1.915* sin(g) + 0.020* sin(2*g); // here I convert g to radians. so g's radians is 70.2485873714
L = q + 1.915* sin(70.2485873714) + 0.020* sin(2*70.2485873714) = 3949.803010038

R = 1.00014 - 0.01671* cos(g) - 0.00014* cos(2*g);
R = 1.00014 - 0.01671* cos(70.2485873714) - 0.00014* cos(2*70.2485873714) = 0.993154006621

e = 23.439 - 0.00000036* d;
e = 23.439 - 0.00000036* 3720.5 = 23.43766044

RA = arctan2(cos(e)* sin(L), cos(L))/ 15;//here I convert e and L to radians.

RA = arctan2(cos(0.4090643366)* sin(68.937066154406), cos(68.937066154406))/ 15
= -0.0109039393163

D = arcsin(sin(e)* sin(L)); // declination of the Sun
D = arcsin(sin(0.4090643366)* sin(68.937066154406)) = -0.070473394414

EqT = q/15 - RA; // equation of time
EqT = q/15 - RA = 3948.05282656/15 - (-0.0109039393163) = 263.21442570998

Dhuhr = 12 + TimeZone - Lng/15 - EqT.
//Lng in my case is 113 East,
I don't know whether I use negative or positive, but I do use -113, if I should use positive,
please tell me, And timezone is +8.

Dhuhr = 12 + 8 - (-113)/15 - 263.21442570998 = -235.64375904332

I don't think the time Dhuhr -235.64375904332 is Julian date. Where am I wrong?

4. Elite Member
Join Date
Feb 2005
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2,160

## Re: How to convert this double prayer time to regular time?

Well, if the map on my wall is correct, 113W (-113) puts you in the Pacific Ocean, a few hundred km off the coast of Baja California Sur, Mexico. 113E (+113) puts you in China a few hundred km from Hong Kong.

As for the rest of it, I can't make much sense of it. I'll take another look at the site you mentioned.

5. Member
Join Date
Jan 2008
Posts
98

## Re: How to convert this double prayer time to regular time?

Is there some Islamic people who can give me a guide!

6. Junior Member
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Jun 2011
Posts
3

## Re: How to convert this double prayer time to regular time?

Hello fantasy,

I am also working on that isue. Have you solved that problem?

kind regards from Germany

7. ## Re: How to convert this double prayer time to regular time?

Originally Posted by martinger
I am also working on that isue. Have you solved that problem?
What "isue" / problem do you mean:
getting a guide from "some Islamic people ..."
or the "Prayer Times Calculation"
or ... what exactly?

8. Junior Member
Join Date
Jun 2011
Posts
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## Re: How to convert this double prayer time to regular time?

Originally Posted by VictorN
What "isue" / problem do you mean:
getting a guide from "some Islamic people ..."
or the "Prayer Times Calculation"
or ... what exactly?
No, sorry.
I want to calculate the Dhuhr time like Fantasy did in the past.
With the same equation I got a similar value like -235.64375904332.
My question is: is this value in minutes, seconds or what? It can't be houres because it should show the Dhuhr time on a specific date (given Julian Date) and on a specific location (depending on Longitude and Latitude).

9. ## Re: How to convert this double prayer time to regular time?

Originally Posted by martinger
No, sorry.
I want to calculate the Dhuhr time like Fantasy did in the past.
With the same equation I got a similar value like -235.64375904332.
Well, if you used "the same equation" the OP had used its
's not surprising that you got "a similar value".

10. Junior Member
Join Date
Jun 2011
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## Re: How to convert this double prayer time to regular time?

Originally Posted by VictorN
Well, if you used "the same equation" the OP had used its
's not surprising that you got "a similar value".

Hi,

well, no. Thanks for that! I've tried to program it by myself .
I will check the code.
I will post the solution asap.

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