*Mini-lecture on manipulating dates in STATA
*Sankari Ayyaluru 8/8/17

clear

*** STEP 1: Input dates ***

gen str8 baselinevis = ""
input
"08/03/17"
"03/22/16"
"06/18/17"
"10/12/16"
"05/30/17"
end
 
list


*** STEP 2: create a new STATA variable called "baselinevisnew" from an old unrecognized date var "baselinevis" ***

gen baselinevisnew = date(baselinevis, "MDY", 2020)
list
 

*** STEP 3: label "baselinevisnew" as a day month and year so you can understand it ***

format baselinevisnew %td
list
*other options available, e.g. %tw, %tm etc.


*** STEP 4: simple addition/subtraction using "baselinevisnew" variable ***

gen followup1 = baselinevisnew + 10
format followup1 %td

gen delta = followup1 - baselinevisnew
list


*** STEP 5: extracting components of dates ***
gen year = year(baselinevisnew)
gen dow = dow(baselinevisnew)  // dow = day of week
list