Is”On board date” different from “Date of sailing”?

During the process of manganese sulfate monohydrate foreign trade, sales assistant would always meet some problems. One of our Pakistan clients opened a L/C to us, which required all the shipping documents specified the “date of sailing”, however, our B/L had only showed the “On board date”. Regarding the L/C requirement policy "All the documents and certificates should keep consistent", “On board date” can be the same with “date of sailing”? 
                  
According to the loading process, “on board date” couldn’t be later than the “date of sailing”. Sometimes, the ship-owners load the cargoes and sail off the ship on the same day, but for most of the ship-owners, the “sailing day” usually comes after “On board date”. More according to UCP 600 items (uniform customs and practice of documentary credit) stipulated: the issued date of B/L is the sailing date. Unless this case that the bill of lading shows “On board date”, then the “On board date is rightly “Date of sailing”.

In this case, our manganese sulfate documentary working to the bank wouldn’t affected by the date discrepancy if the BL showed on board date.