《北史·列传·卷七十七》
夏至阴始，祭祀地的时辰，就是皇后的本命，这是喜庆之五。
夏至阴始，祀地之辰，即是皇后本命，此庆五也。
Yin began at the Summer Solstice, the hour of the sacrifice in the Altar of the Earth was the birthday of the empress, this was the fifth joy.
<s>[INST] Identify the key themes in this Classical Chinese text and explain them in English: 夏至阴始，祀地之辰，即是皇后本命，此庆五也。 [/INST] Yin began at the Summer Solstice, the hour of the sacrifice in the Altar of the Earth was the birthday of the empress, this was the fifth joy.</s>
Identify the key themes in this Classical Chinese text and explain them in English: 夏至阴始，祀地之辰，即是皇后本命，此庆五也。
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Yin began at the Summer Solstice, the hour of the sacrifice in the Altar of the Earth was the birthday of the empress, this was the fifth joy.
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