Getting Started with SAS Programming

Chapter 13: Working with SAS Dates

Introduction

SAS can read and write dates in almost any format, such as 5/23/2015 or 23May2015. No matter how the date appears in the input file, SAS converts all dates to the number of days from January 1, 1960. Thus, January 1, 1960 is 0; January 2, 1960 is a 1; and so on. Dates before January 1, 1960 are converted to negative numbers. For example, December 31, 1959 is equal to -1. Almost all computer languages store dates as the number of days from a fixed date. SAS chose January 1, 1960—other languages use other dates. Although SAS dates are stored internally as numbers, SAS can display the date in any of the standard formats. For those readers interested in history, SAS does not compute dates before January ...