I am just learning mining process. Today I learned that we have to find nonce for given block header.

And for block header we need timestamp in UTC

I took the timestamp data from below link of 125552 block https://www.blockchain.com/btc/block/00000000000000001e8d6829a8a21adc5d38d0a473b144b6765798e61f98bd1d

And used the below linke to convert it from UTC to seconds https://www.epochconverter.com/

And I am getting 1305998760

But according to the example in the below link its 1305998791 https://en.bitcoin.it/wiki/Block_hashing_algorithm

And what is endian in the above link

Can anyone please help me what am I missing

Thanks in advance