To set the stage for the explanation below, it's important to note that formulas in Airtable are slightly different from formulas in a traditional spreadsheet program. In a spreadsheet, you can put a formula in any cell, and have it reference any other cell in the sheet (i.e. the row above). Airtable is a relational database so formulas are applied for the entire field (what Airtable calls a column) so that the same formula applies to every record in that field.
In this case, trying to build the desired workflow would involve using linked records (Linked record fields), lookup fields (Guide to formula, lookup, rollup, and other computed fields), and formula fields (Formula field reference) to almost get the desired result. The goal for this approach would be to pass the end date-time from one record on to the next (linked) record as the start date-time. Additionally, a duration field would be used to calculate the end date-time from the start date-time of that same record.
That last step, though, creates something called a circular reference -- basically an infinite formula loop which would likely crash your table. Because of this, Airtable doesn't allow these to be created.
I would recommend using a Gantt view instead, as you can accomplish something similar to what you're looking to do by using dependencies and adjusting task dates within the Gantt chart itself. The one catch here is that both the start and end date fields should be manual -- not formulas. As soon as you use formulated date fields in a Gantt chart, you can no longer click and drag projects to change their date values.
More info at the following links:
Designing linked records and dependencies