Notes
code 100 used for <1 day ago, code 101 used for Days: 1, code 201 used for weeks: 1, code 301 used for months: 1, code 399 used for months missing, code 401 used for yeasr: 1, code 995 used for Within last 4 weeks, code 996 used for Before last birth, and code 997 used for Inconsistent, while code 998used for Don't know