but this will be useful anyway ..
https://www.opencart.com/index.php?rout ... on_id=3369
This is a ‘tutorial’ for adding date column - similar - you could do it from that
https://isenselabs.com/posts/how-to-add ... pencart-2x
A formatted version of the above - it should be easier to follow and it is tested and it works.
You should not modify core files .. if you would like to donate a cup of coffee I will write it in a modification for you.
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Try to convert for2.x and you will have like this
https://www.opencart.com/index.php?rout ... n_id=22953
https://www.opencart.com/index.php?rout ... n_id=10787
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