Weapons mentioned in Indian texts can be classified into two. Astra,the weapons that are effective with Mantra. Sastra, traditional weapons like Sword,Spear.
Sahadeva fixed it and Krishna manipulated the Solar Eclipse to happen a Day earlier, knowing well it was started on the Day of Solar Eclipse the one who chooses that date would win. Duryodhana was tricked into fixing this date. This day was not the Amavasya, when Solar Eclipse happens, but a Day earlier. This Amavasya is called the Bodhayana Amavasya.