Translating values over time

Hi everybody.
I have a complicated math problem. As follows:
At the time points: 00:00, 00:05, 00:10, 00:15,....(multiple of 5), the data before and after does not change.
In addition to the above milestones, it changes, based on the time of 2 landmarks.
Please see attached file.
Can someone research and help me solve this complex problem.
Thank you.