In [6]: df = DataFrame({'A' : [pd.Timedelta('1 day 1 sec')],'B' : [5], 'C' : [pd.Timestamp('20130101') ]}) In [7]: df Out[7]: A B C 0 1 days 00:00:01 5 2013-01-01 In [8]: df.dtypes Out[8]: A timedelta64[ns] B int64 C datetime64[ns] dtype: object In [9]: df[['A']].to_json() Out[9]: '{"A":{"0":86401000}}' In [10]: df.to_json(default_handler=lambda x: x.asm8) Out[10]: '{"A":{"0":86401000000000},"B":{"0":5},"C":{"0":1356998400000}}' In [11]: df.to_json() OverflowError: Maximum recursion level reached