halcyon

a very happy or successful period in the past (often + of ) She recalled the halcyon days of childhood. That was in the halcyon days of the 1980's when the economy was booming.

A calm and peaceful period of time. There was an old belief that two weeks of calm weather were to be expected just before and after the winter solstice, when the halcyon bird (a species akin to the kingfisher) calmed the sea in order to lay and hatch her eggs on a floating nest. That idea originated with the Greek myth of Alcyone, daughter of Aeolus, god of the winds, who was married to the king of Thessaly. When the king was drowned at sea, Alcyone threw herself into the water in her grief. However, the gods transformed her into the halcyon bird whom the wind carried to be reunited with her husband.