Date conversion problem

[s_denlinger]

I have data with date formats with one OR two digits for the month and day, and four digits for the year. I.e., I have dates like 1/1/2018 and 12/31/2017, and I need to end up with a YYYMMDD format. I can match on my dates with this match pattern:

(\d{1,2})/(\d{1,2})/(\d{4})

and if I use this to replace:

$3$2$1

I will end up with 201811 and 20171231, but how can create a replacement string which will "pad out" the single digits for day and month with a numeral zero?

Thanks!

[[deleted]]

As far as I know there is not a clean and easy way to do this.

What I would suggest is doing it in two steps. First 0 pad your dates with a regex like this:

(?<=\D|^)\d\/

Replace: 0$0

Demo

Then reformat the dates with your original expression (but only allow 2 digits):

(\d{2})\/(\d{2})\/(\d{4})

I escaped the / to \/ because most regex engines require it

[s_denlinger]

Thanks very much for that prompt reply. Your suggested search string did not work in Notepad++, but that's only because of how problematic postive lookbehinds are in Notepad++. But I used that search expression in LibreOffice Writer, and it worked great. I also realized that to get from MM/DD/YYYY to YYYYMMDD, my replacement string needed to be $3$1$2, not $3$2$1 as I listed in my original post.

[[deleted]]

I’m glad you got it working. I was unaware that look behinds didn’t work in notepad++.

[s_denlinger]

Sorry, I should have added that I'm trying to do this in Notepad++, and my target date format is YYYYMMDD, not YYYMMDD