Time capsule from 1968 to be opened this year in September

The video discusses a stainless steel monument commemorating the 100th anniversary of discovering helium. It features four Tyme Castle columns containing books, artifacts, and documents to educate future generations about life in 1968. Helium is used to preserve these items. The capsules are scheduled to be opened at different intervals, with the first opened in 1990 and others set for future dates.

What types of items are stored in the Tyme Castle columns?

What is the timeline for opening the capsules mentioned in the text?