There’s a solar eclipse that’ll cut a path across Mexico and the eastern United States coming on April 8th, 2024 and there’s a good chance the glasses you bought for this year’s eclipse will still work even if they have an expiration date. It’s easy to tell if your eclipse glasses will still be good by checking their ISO standard number.
Solar eclipse glasses that are ISO 12312-2 complaint don’t have an expiration date even if one is printed on their packaging. According to NASA,
If your eclipse glasses or viewers are compliant with the ISO 12312-2 safety standard, you may look at the uneclipsed or partially eclipsed Sun through them for as long as you wish. Furthermore, if the filters aren’t scratched, punctured, or torn, you may reuse them indefinitely. Some glasses/viewers are printed with warnings stating that you shouldn’t look through them for more than 3 minutes at a time and that you should discard them if they are more than 3 years old. Such warnings are outdated and do not apply to eclipse viewers compliant with the ISO 12312-2 standard adopted in 2015.
Considering the team at NASA knows what they’re talking about I’m debating if I should keep my solar eclipse glasses safely tucked away until 2024 or donate them to a local school. Either way, mine won’t be going into the trash because they still have years of good use left in them.