# SP 2013 List Validation: enforce sequential dates

I'm having formula and logic trouble getting a list validation formula that will force the user to enter four dates in sequential order. I have Date1, Date2, Date3, and Date4. I also need to skip a calculation if a "later" date is blank.

I would be grateful for help. Thanks-

• Could you provide example for "skip calculation"? Are these valid entries: [09/22/2020, 09/23/2020, Blank, 09/24/2020]; [09/23/2020, Blank, 09/24/2020, Blank]? – Matiur Rahman Sep 22 '20 at 17:13
• Hi Matiur. I am sorry for the confusion. I need the validation to only work (for example) on Date2 when Date1 has a date, or on Date3 when Date2 has a date. So, if the previous date field has a data value, the most recently filled date in the sequence gets the validation. Thank you! – ChasEpes Sep 22 '20 at 21:15
• posted my answer. Let me know your feedback or if you have any questions – Matiur Rahman Sep 27 '20 at 18:32

``````=IF(AND(NOT(ISBLANK(Date1)),NOT(ISBLANK(Date2))),IF(DATEDIF(Date1,Date2,"D")=1,IF(AND(NOT(ISBLANK(Date2)),NOT(ISBLANK(Date3))),IF(DATEDIF(Date2,Date3,"D")=1,IF(AND(NOT(ISBLANK(Date3)),NOT(ISBLANK(Date4))),IF(DATEDIF(Date3,Date4,"D")=1,TRUE,FALSE),TRUE),FALSE),IF(AND(NOT(ISBLANK(Date3)),NOT(ISBLANK(Date4))),IF(DATEDIF(Date3,Date4,"D")=1,TRUE,FALSE),TRUE)),FALSE),IF(AND(NOT(ISBLANK(Date2)),NOT(ISBLANK(Date3))),IF(DATEDIF(Date2,Date3,"D")=1,IF(AND(NOT(ISBLANK(Date3)),NOT(ISBLANK(Date4))),IF(DATEDIF(Date3,Date4,"D")=1,TRUE,FALSE),TRUE),FALSE),IF(AND(NOT(ISBLANK(Date3)),NOT(ISBLANK(Date4))),IF(DATEDIF(Date3,Date4,"D")=1,TRUE,FALSE),TRUE)))