Opensource ERP with custom work hours for employees?

Question

ERP

We need an open source solution that can
flexibly adjust the working hours of employees. Each employee has a completely floating, but predetermined schedule, often without patterns.
- at a primitive level, operate with tasks, estimates and accounting for the time spent. Based on the assignee, estimate and employee schedule - draw conclusions about when this task will be done.
Share, please, if you met such a miracle?

Answer 1

Redmine + Plugins
This is not ERP, but what you need to do can.