title: Create date of "X" column, when I have age in days at "X" column and birth date column in R
body: <p>I'm having some trouble finding out how to do a specific thing in R.</p>
  <p>In my dataset, I have a column with the date of birth of participants. I also have a column giving me the age in days at which a disease was diagnosed.</p>
  <p>What I want to do is to create a new column showing the date of diagnosis. I'm guessing it's a pretty easy thing to do since I have all the information needed, basically it's birth date + X number of days = Date of diagnosis, but I'm unable to figure out how to do it.</p>
  <p>All of my searches give me information on the opposite, going from date to age. So if you're able to help me, it would be much appreciated!</p>