A cosmological decade ( CÐ ) is a division of the lifetime of the cosmos. The divisions are logarithmic in size, on base 10.

As expressed in log( Seconds per Ðecade )

When CÐ is measured in log( seconds/Ð ), the epoch CÐ -43.2683307 was 10**(-43.2683307) seconds, the Planck time since the big bang. CÐ 7.3230203 is 1 year = 365.2564 mean solar days. The epoch CÐ 17.6355 has lasted 10**(17.6355) seconds = 13.7 billion years since the big bang. There have been 60.9 cosmological decades between the Planck epoch, CÐ -43.2683307, and the current epoch, CÐ 17.6355.

• CÐ 1 lasts 10 seconds
• CÐ 100 lasts 10¹⁰⁰ seconds.

The 100th cosmological decade lasts from 10¹⁰⁰ to 10¹⁰¹ seconds after Time Zero (Big Bang event). CÐ - is Time Zero.

As expressed in log( Years per Ðecade )

Fred Adams & Greg Laughlin, (1997), in The Five Ages of the Universe (http://archive.ala.org/booklist/v95/adult/ap2/16adams.html) first defined the cosmological decade as expressed in log years per decade. To convert to this format, simply divide by seconds per year; in logarithmic terms, simply subtract 7.3230203 from the values listed above. Thus when CÐ is expressed in log(years/Ð), the Planck time could also be expressed as 10**(-43.2683307 - 7.3230203) years = 10**( -50.5913510 ) years.

In this definition, the current epoch is CÐ 17.6355 - 7.3230203 = 10.3125 cosmological decades. As before, there have been 60.9 cosmological decades between the Planck epoch and the current epoch. In this definition, in the 100th cosmological decade, there are 10**100 years.

In their view, the history of the universe can be segmented into 5 Ages: