Possible Clues:

• Rotten old peach, days out of date
• Historically significant
• English friend goes round old church that is historically significant
• Era-defining
• Of a historic period
• Referring to important era, old, in rebuilt chapel
• Highly significant in bringing about change
• Of a geological or historical period
• Marking the beginning of a new era
• Relating to a particular time, historical or geological perhaps