Stata: Gaps between dates - stata

Question

I have a situation where I need to need to order several dates to see if there is a gap in coverage. My data set looks like this, where id is the panel id and start and end are dates.
id start end
a 01.01.15 02.01.15
a 02.01.15 03.01.15
b 05.01.15 06.01.15
b 07.01.15 08.01.15
b 06.01.15 07.01.15
I need to identify any cases where there is a gap in coverage, meaning when the 2nd start date for an id is greater than the first end date for the same id. Also it should be noted that the same id can have undetermined number of observations and they might not be in a particular order. I wrote the code below for a case where there are only two observations per id.
bys id: gen y=1 if end < start[_n+1]
However, this code does not produce the desired results. I'm thinking that there should be another way to approach this problem.

Answer 1

Your approach seems sound in essence, assuming that your date variables are really Stata daily date variables formatted suitably. You don't explain at all what "does not produce the desired results" means to you.
The code below creates a sandbox similar to your example, but with string variables converted to daily dates.
Key details include:
Observations must be sorted by date within panel.
The end date for the observation after the last in each panel would always be returned as missing, and so as greater than any known date. The code here returns the corresponding indicator as missing.
clear
input str1 id str8 (s_start s_end)
a "01.01.15" "02.01.15"
a "02.01.15" "03.01.15"
b "05.01.15" "06.01.15"
b "07.01.15" "08.01.15"
b "06.01.15" "07.01.15"
b "10.01.15" "12.01.15"
end
foreach v in start end {
gen `v' = daily(s_`v', "DMY", 2050)
format `v' %td
}
// the important line here
bysort id (start) : gen first = end < start[_n+1] if _n < _N
list , sepby(id)
+----------------------------------------------------------+
| id s_start s_end start end first |
|----------------------------------------------------------|
1. | a 01.01.15 02.01.15 01jan2015 02jan2015 0 |
2. | a 02.01.15 03.01.15 02jan2015 03jan2015 . |
|----------------------------------------------------------|
3. | b 05.01.15 06.01.15 05jan2015 06jan2015 0 |
4. | b 06.01.15 07.01.15 06jan2015 07jan2015 0 |
5. | b 07.01.15 08.01.15 07jan2015 08jan2015 1 |
6. | b 10.01.15 12.01.15 10jan2015 12jan2015 . |
+----------------------------------------------------------+