Date of conception from the date of birth

[Gaurav Dhamija]

I know the date, month and year of birth for children in a locality. However, I want to calculate the date of conception from this information. I don't have the exact information on the gestation period. However, I am planning to use 38 weeks (266 days) as an approximation of a normal-term pregnancy (gestation period), as per the World Health Organization definition.

Here is the sample data for your reference:

input byte date float mob int year float gestation_period_days
15 11 2001 266
4 8 2001 266
13 7 2001 266
15 3 2002 266
4 7 2001 266
21 6 2001 266
1 1 2002 266
11 11 2001 266
23 9 2001 266
13 9 2001 266
30 6 2001 266
25 4 2002 266
13 10 2001 266
21 11 2001 266
6 7 2001 266
22 6 2001 266
9 7 2001 266
15 2 2002 266
6 1 2002 266
24 12 2001 266
4 12 2001 266
3 2 2002 266
22 11 2001 266
19 12 2001 266
22 11 2001 266
4 9 2001 266
28 8 2001 266
12 1 2002 266
24 7 2001 266
12 10 2001 266
5 8 2001 266
14 4 2002 266
1 9 2001 266
20 5 2001 266
4 3 2002 266
31 8 2001 266
4 6 2001 266
15 12 2001 266
9 12 2001 266
11 10 2001 266
2 11 2001 266
2 5 2002 266
15 10 2001 266
21 7 2001 266
1 11 2001 266
25 11 2001 266
26 10 2001 266
12 4 2002 266
3 4 2002 266
4 10 2001 266
5 1 2002 266
16 3 2002 266
15 8 2001 266
2 8 2001 266
21 11 2001 266
3 5 2002 266
15 11 2001 266
6 1 2002 266
23 8 2001 266
13 11 2001 266
12 5 2002 266
25 11 2001 266
27 10 2001 266
15 10 2001 266
8 1 2002 266
12 3 2002 266
1 8 2001 266
4 11 2001 266
25 3 2002 266
7 7 2001 266
12 8 2001 266
16 4 2002 266
3 5 2002 266
1 9 2001 266
10 1 2002 266
10 3 2002 266
8 5 2002 266
7 8 2001 266
4 12 2001 266
3 5 2002 266
20 10 2001 266
4 5 2002 266
12 11 2001 266
25 12 2001 266
11 3 2002 266
26 6 2001 266
18 1 2002 266
14 2 2002 266
28 3 2002 266
31 3 2002 266
10 12 2001 266
26 1 2002 266
7 6 2001 266
11 2 2002 266
11 12 2001 266
2 2 2002 266
18 3 2002 266
15 12 2001 266
27 10 2001 266
20 12 2001 266
end

It would be great if someone could guide me to calculate the date of conception from this information.

Thanks in advance.

[Øyvind Snilsberg]

gen wanted = mdy(mob,date,year) - 266

[Gaurav Dhamija]

Thanks @Øyvind Snilsberg
I am not familiar with what I am getting after executing this code. I know it is number of days. However, I don't know what is the reference from which it is giving these days. It would be great if you could also tell me how to convert this 'wanted' variable into date of conception, month of conception and year of conception.

[Øyvind Snilsberg]

it is the number of days since January 1, 1960,

format %td wanted

date, month and year of conception,

g doc = day(wanted)
g moc = month(wanted)
g yoc = year(wanted)

[Gaurav Dhamija]

Thanks @Øyvind Snilsberg. It's done.