How to convert time stamp into relative time

[vb00494773]

Hi Team,

Please help to convert the timestamp into relative time

below is the sample data:

date                                   value

11/14/2016 18:20:10.960		1411262.667
11/14/2016 18:20:10.970		1411279.167
11/14/2016 18:20:10.980		1411295.667
11/14/2016 18:21:10.990		1411312.167
11/14/2016 18:20:11.000		1411328.667
11/14/2016 18:20:11.010		1411345.167
11/14/2016 18:22:11.020		1411361.667
11/14/2016 18:20:11.030		1411378.167
11/14/2016 18:20:11.040		1411394.667
11/14/2016 18:23:12.980		1414381.167
11/14/2016 18:20:12.990		1414397.667
11/14/2016 18:20:13.000		1414414.167
11/14/2016 18:24:13.010		1414430.667
11/14/2016 18:20:13.020		1414447.167
11/14/2016 18:20:13.030		1414463.667
11/14/2016 18:25:13.040		1414480.167
11/14/2016 18:20:14.980		1417549.167
11/14/2016 18:26:14.990		1417565.667
11/14/2016 18:20:15.000		1417582.167
11/14/2016 18:27:15.010		1417598.667
11/14/2016 18:20:15.020		1417615.167
11/14/2016 18:20:15.040		1417631.667
11/14/2016 18:28:15.050		1417648.167

Out put should be like below :

by using timestamp, i should get the x-axis as relative time (whole time stamp need to convert into seconds)

FYI, starting time stamp should be consider as 0 (zero) then 300 seconds need to add for the starting time like that it should go in x-axis .

(starting time - (minus ) next time difference in seconds need to add into the relative time .

Thanks,

Venkatesh