第一个that是代词,that was the day是那天
第二个that应该是定语从句引导词,定the day
第三个that是宾语从句的引导词,后面是宾语
整个句子是主句加上两个从句嵌套而成
That was the day 是主句
that I learned for all time 是定从
no creatures of fable and fantasy are half as nice as the creatures of real life是学到的东西,是定语从句中的宾语从句