Describes the working time for a day. It supports 3 intervals for now.
| Column | Type | References | Comments |
| id | Integer | Primary key | |
| vdb_id | Integer | ||
| calendar_id | Integer | db_working_calendar.id | ID of the working calendar this record belongs to |
| s1_from | Integer | Start time in minutes of the 1st interval. | |
| s1_to | Integer | Finish time in minutes of the 1st interval. | |
| s2_from | Integer | Start time in minutes of the 2nd interval. | |
| s2_to | Integer | Finish time in minutes of the 2nd interval. | |
| s3_from | Integer | Start time in minutes of the 3rd interval. | |
| s3_to | Integer | Finish time in minutes of the 3rd interval. | |
| dow | Integer | Day of week this working time refers to. 1 for Sunday, 2 for Monday, etc. |