Using the ANSI or CSA standards to determine approximate Date of Manufacture.
Most manufacturers today are required to include the manufacture compliance standard on the data tag. For the U.S. the compliance standard is typically from the American National Standards Institute (ANSI). For Canada, a common standard compliance is through the Canada Standards Association Group (CSA). Many times both standards are listed. Regardless, the specific standard will normally be listed on the data tag/plate and followed by the YEAR of the last revision (often the year is placed in parenthesis or follows the hyphen after the specific standard number). As these standards are revised or renewed approximately every 4 to 6 years, one can reasonably estimate the year of manufacture within 4-6 years from (after) the standards date.