关于date of commencement

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信用证下，受益人提交的租船提单显示SHIP ON BOARD DATE: APRIL 3, 2014。
提交的保险单（INSURANCE POLICY）显示：

1、DATE OF ISSUE: APRIL 9, 2014

2、DATE OF COMMENCEMENT:
         (1) LOADING PERIOD: FROM MAR 20, 2014 TO APRIL 3, 2014
         (2) SLG ON/ABT: APRIL 3, 2014
         IN LOCAL STANDARD TIME AS AT THE LOCATION OF THE LOSS, DAMAGE OR OCCURRENCE.
请教该保险单的生效日期是哪天？