Formulas – Google Sheets referencing a cell adjacent to a cell on another sheet

I have a schedule in Google sheets with each cell referencing a cell value retrieved from the weekly sheets. I would like to be able to enter the cell reference for the first of the month, then have the rest of the dates fill automatically from that date. For example, the first of the month would be referenced as
= (& # 39; 4/01/19 & # 39; A12), the adjacent cell would then indicate "4/01/19"! B12, where the values ​​of the 2nd of the month have been entered. As the names of leaves naturally vary from week to week and from month to month, I basically try to do something like:

a1 = & # 39; & # 39 ;! sheet1 a1
b1 = offset (the-cell-being-referenced-in-a1,0,1)

Is it possible?

Link to an example of the document:
https://docs.google.com/spreadsheets/d/1aHLX8LcVpefi9mxHVeU_H6jB97RDhb4_eKD2h39FDzA/edit?usp=sharing