What is the governing valuation date when the equivalent of a wrongfully taken fungible item perishes?

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When a fungible item perishes and its equivalent is unavailable, the value due is assessed based on the day the equivalent was no longer available. However, supporting evidence from Imam Ahmad suggests that for items taken without the owner's permission (like stipulated measurements), the value is considered on the day of the usurpation, which implies the valuation date should be the day the item was taken. A distinction is made where if the usurper took the item with the owner's permission and gained ownership rights, the value is set upon his acquisition of ownership. In cases of pure usurpation, the monetary value is established in the debt only on the day of its loss or the impossibility of returning its equivalent, hence it is assessed at that time.