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Problem with dates in the Ethiopia datasets [message #66] Wed, 20 February 2013 11:19 Go to next message
DHS user is currently offline  DHS user
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Registered: February 2013
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The variables in the Ethiopia datasets, related to the year of the study do not match the actual timing of the study. Is this an error?
Re: Problem with dates in the Ethiopia datasets [message #67 is a reply to message #66] Wed, 20 February 2013 11:28 Go to previous messageGo to next message
Bridgette-DHS is currently offline  Bridgette-DHS
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All standard date variables in the Ethiopia data file are in the Ethiopian calendar. In general the Ethiopian calendar is 92 months behind the Gregorian (western) calendar. The Ethiopian year runs from September 11 through September 10 and has 12 months of 30 days and 1 months of 5 days. Thus it is only possible to transfer the Ethiopian calendar into the Gregorian calendar when the exact date (day, month and year) is available. Therefore, in the file you will find additional variables indicating the Gregorian dates if they could be established.

Note that all standard variables based on calendar dates and century month codes are given in the Ethiopian Calendar. In general, the Ethiopian year consists of 365 days, divided into 12 months of 30 days and one month of 5 days (6 days in a leap year). Ethiopia's new year falls on September 11and ends the following September 10 according to the Gregorian calendar. From September 11 to December 31, the Ethiopian year runs seven years behind the Gregorian year, thereafter, the difference is eight years. Since the exact day is not available for most dates, it is not possible to convert the dates exactly, but only approximate it to the month. There is a difference of 92 months between the two date systems. The 13th month of the Ethiopian calendar falls in September. Thus, to keep the higher precision available in the Ethiopian calendar, these were used for all standard recode variables where applicable. In general, dates in the Gregorian calendar are provided as country specific variables. However, the calendar is transferred to the Gregorian calendar.

To explain somewhat further, the number of months in the CMC variables (even for Ethiopian dates) are computed as follows: each year has 12 months, but when the event was in the 13th month then 13 is added for the number of months. Thus e.g. a person was born in the 13th month of 1960 in the Ethiopian calendar, then the CMC is 60 * 12 + 13. Thus the 5 days in the 13th month really go to the following year when you recomputed the CMC back to years (with 12 months). But this will cause little bias. So just use the CMC as you would for other surveys (intervals should not be divided by 13, but by 12). However, know that on average the Ethiopian calendar lags 92 months behind our Gregorian system.

The Ethiopian calendar was kept as the standard variables, sinceĀ  not all dates (e.g. vaccination dates) could be transferred.

Here is a link that you can use to convert Ethiopian dates:

http://www.funaba.org/en/calendar-conversion.cgi

Attached is a little Stata script: "ETcalconvert", that you may find useful (written by DHS Data User: Keith Kranker).

I hope this helps.

Bridgette-DHS

[Updated on: Mon, 18 March 2013 09:14]

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Re: Problem with dates in the Ethiopia datasets [message #8980 is a reply to message #67] Fri, 22 January 2016 12:02 Go to previous messageGo to next message
lillo?S is currently offline  lillo?S
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Hello,

From what I can see in the DHS 2005 there are country-specific variables that define the dates in the Gregorian calendar, the same does not hold for DHS 2011.

In the 'Individual Recode Documentation' (p.8) I find this:

"Before the production of any indicators with these data the Ethiopian calendar was converted to the Gregorian calendar but conserving the Ethiopian year; however, the Ethiopian first month is considered in the logic as January, the 2nd as February, etc. For dates including year, month and day the conversion is precise since both calendars have 365 or 366 days; for dates including only year and month, the 13th month was included in December."

I understand that the months have already been converted, whereas the years have not.
When I go to the 'CSPRO Process Summary' file and look at v006, the months of interview range from 4 through 9. According what's written in the IRD word file, I should interpret this as 4=April and 9=September because the conversion is supposed to have been already done. However, in the website at http://dhsprogram.com/what-we-do/survey/survey-display-359.c fm I see that: Fieldwork: December 2010 - May 2011. These months do not match the ones above, whereas they could coincide if the conversion had not been done.

My questions are:

1- has the conversion been done or not?
2- how are the CMC variables given?

Thanking you in advance.
Re: Problem with dates in the Ethiopia datasets [message #8981 is a reply to message #67] Fri, 22 January 2016 12:04 Go to previous messageGo to next message
lillo?S is currently offline  lillo?S
Messages: 15
Registered: December 2015
Member
Hello,

From what I can see in the DHS 2005 there are country-specific variables that define the dates in the Gregorian calendar, the same does not hold for DHS 2011.

In the 'Individual Recode Documentation' (p.8) I find this:

"Before the production of any indicators with these data the Ethiopian calendar was converted to the Gregorian calendar but conserving the Ethiopian year; however, the Ethiopian first month is considered in the logic as January, the 2nd as February, etc. For dates including year, month and day the conversion is precise since both calendars have 365 or 366 days; for dates including only year and month, the 13th month was included in December."
I understand that the months have already been converted, whereas the years have not.

When I go to the 'CSPRO Process Summary' file and look at v006, the months of interview range from 4 through 9. According what's written in the IRD word file, I should interpret this as 4=April and 9=September because the conversion is supposed to have already been done. However, in the website at http://dhsprogram.com/what-we-do/survey/survey-display-359.c fm I see that: Fieldwork: December 2010 - May 2011. These months do not match the ones above, whereas they could coincide if the conversion had not been done.

My questions are:

1- has the conversion been done or not?
2- how are the CMC variables given?

Thanking you in advance.
Re: Problem with dates in the Ethiopia datasets [message #9035 is a reply to message #8981] Fri, 29 January 2016 12:56 Go to previous messageGo to next message
Bridgette-DHS is currently offline  Bridgette-DHS
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Registered: February 2013
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Following is a response from Senior DHS Stata Specialist, Tom Pullum:

In the 2011 survey, all dates are in the Ethiopian calendar rather than the Gregorian calendar. The cmc is also calculated consistently with the Ethiopian calendar. For example, you can confirm that v008=12(v007 1900) + v006. This consistency is found in all surveys, whether using the Gregorian, Ethiopian, or Nepalese calendars.

To convert to the Gregorian calendar, add 92 to the Ethiopian cmc. Then get the Ethiopian year and month from the Ethiopian cmc as follows, illustrated again for v006, v007, and v008:

gen v007=int((v008-1)/12)
gen v006=v008-12*v007
replace v007=v007+1900
Re: Problem with dates in the Ethiopia datasets [message #9179 is a reply to message #9035] Fri, 19 February 2016 10:12 Go to previous messageGo to next message
st89
Messages: 1
Registered: February 2016
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A follow-up question about the dates in the 2011 survey (specifically the children's recode): variable h9d (day of month of measles vaccination, if known) takes on values from 1 to 31. However, my understanding is that all of the dates are in the Ethiopian calendar, which should have 12 months of 30 days + one month of 5 or 6 days. I'm unclear on how to use h9d values of 31 since it is not in the Ethiopian calendar, and am thus not able to convert the three variables h9y-h9m-h9d to Gregorian dates.

Thanks for your help!
Re: Problem with dates in the Ethiopia datasets [message #9183 is a reply to message #9179] Fri, 19 February 2016 12:02 Go to previous messageGo to next message
Bridgette-DHS is currently offline  Bridgette-DHS
Messages: 1167
Registered: February 2013
Senior Member
Another response from Tom Pullum:

I will start by repeating an answer I gave on the forum on January 29, but this time with a correction of a typo in the January 29, version, where in the second paragraph I said "Ethiopian" but meant "Gregorian"--sorry about that.

In the 2011 survey, all dates are in the Ethiopian calendar rather than the Gregorian calendar. The cmc is also calculated consistently with the Ethiopian calendar. For example, you can confirm that v008=12(v007 1900) + v006. This consistency is found in all surveys, whether using the Gregorian, Ethiopian, or Nepalese calendars.

To convert to the Gregorian calendar, add 92 to the Ethiopian cmc. Then get the Gregorian year and month from the Gregorian cmc as follows, illustrated again for v006, v007, and v008. I will use vg006, etc, to indicate that these are Gregorian versions of the original Ethiopian codes.

gen vg008=v008+92
gen vg007=int((vg008-1)/12)
gen vg006=vg008-12*v007
replace vg007=vg007+1900

Now to get to your question. Although you may be right that there is a 5-day month in the Ethiopian calendar, I think it must be absorbed in one or both of the adjacent months. If you go to the BR file and enter "tab h9m" or "tab b2", etc., you will see 12 numbered months, all with about the same number of cases. I recommend that you simply do the month and year conversion described above, but keep the day as h9d. I would look at how the days 29, 30, and 31 are converted to a day with "day=mdy(h9m,h9d,h9y)". You will find that certain combinations of year and month and day (even year, because of Leap Year) are rejected, and will produce "day=." because the specified Gregorian month has only 30 days, or in the case of February has only 28 days, except in a Leap Year, when it has 29! (Ten days from now we will have a Feb. 29!) Then I personally would recode h9d for all of the rejected values to 28, but you could go to more trouble and successively convert to 30, then to 29, then to 28, until all combinations of year, month, and day are accepted. The kind of error that will be incurred with this sort of adjustment will be trivial, especially compared with other reporting errors.

Re: Problem with dates in the Ethiopia datasets [message #13551 is a reply to message #9183] Fri, 17 November 2017 12:39 Go to previous message
kcaglaya@tulane.edu is currently offline  kcaglaya@tulane.edu
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Registered: November 2017
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Hi,

I use b1 (month of birth) and hw16 (day of birth of child) in my analysis and initially assumed that both of these information are provided according to the Ethiopian calendar. However, as mentioned before in the forum; hw16 takes the values from 1 to 31 in 2011 and 2016 Surveys. (In 2000 and 2005 max value for hw16 is 30) I looked at the months in which hw16 is equal to 31 and this is how it looks like:

. tab b1 if hw16==31

month of |
birth | Freq. Percent Cum.
------------+-----------------------------------
1 | 37 24.03 24.03
3 | 21 13.64 37.66
5 | 25 16.23 53.90
7 | 19 12.34 66.23
8 | 30 19.48 85.71
10 | 16 10.39 96.10
12 | 6 3.90 100.00
------------+-----------------------------------
Total | 154 100.00

These are the Gregorian months with 31 days. Does this mean that b1 (month of birth) is also in Gregorian calendar? Also see the months with 30 and 31 days:

. tab b1 if hw16==31 | hw16==30

month of |
birth | Freq. Percent Cum.
------------+-----------------------------------
1 | 73 14.07 14.07
3 | 52 10.02 24.08
4 | 32 6.17 30.25
5 | 67 12.91 43.16
6 | 38 7.32 50.48
7 | 72 13.87 64.35
8 | 59 11.37 75.72
9 | 27 5.20 80.92
10 | 52 10.02 90.94
11 | 26 5.01 95.95
12 | 21 4.05 100.00
------------+-----------------------------------
Total | 519 100.00

It lacks February as we expect from the Gregorian Calendar.

My conversion from Ethiopian to Gregorian calendar depends on b1. I would greatly appreciate a clarification regarding the variable b1.

Regards,

Koray Caglayan
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