GST refund

(2) relevant date means-
(a) in the case of goods exported out of India where a refund of tax paid is available in respect of goods themselves or, as the case may be, the inputs or input services used in such goods,
(i) if the goods are exported by sea or air, the date on which the ship or the aircraft in which such goods are loaded, leaves India; or
(ii) if the goods are exported by land, the date on which such goods pass the frontier; or
(iii) if the goods are exported by post, the date of despatch of goods by the Post Office concerned to a place outside India;

Means date of B/L????