Related Clues:

• Longest division of geological time
• Time measured in ages
• Geologist's division
• Countless centuries
• Awfully long time
• Geologic period
• Unbelievably long time
• It goes on and on
• Geologic time
• Longish time span
• L-o-n-g time period
• A really long time
• Long period
• A very long time
• It's a stretch