Short answer. Coverage of the employer starts on the first day of operation, while coverage of the employee starts on the date of employment. Article 170 ties each side's coverage to its own starting event rather than to a single shared date.
What the law says
Compulsory coverage of the employer during the effectivity of this Title shall take effect on the first day of his operation, and that of the employee, on the date of his employment.
Labor Code, Article 170 — When Coverage Takes Effect. Read the full provision →
Two separate coverages, two separate dates
Article 170 does not describe a single coverage date shared by employer and employee alike. It sets two: compulsory coverage of the employer takes effect on the first day of his operation, while coverage of the employee takes effect on the date of his employment. These are distinct starting points tied to two different events — one marking when the business itself began operating, the other marking when a particular employee began working.
The employer's coverage starts with the business itself
For the employer, the trigger is the first day of his operation — the point at which the business began operating at all. This is not tied to when any particular worker was hired; it is tied to the existence of the operating business itself, which is what brings the employer within compulsory coverage under this Title from that first day forward.
The employee's coverage starts with the employment itself
For the employee, the article ties coverage to something more personal: the date of his employment. Coverage for a given employee begins when that employee's own employment begins, not on some later date tied to paperwork, probation, or anything else. The date the person actually became an employee is what Article 170 uses as the starting point for that individual's coverage. This automatic start date is separate from the age limit in Article 168, which makes compulsory coverage apply to employers and employees not over sixty years old, with a specific exception for an employee over sixty who is paying contributions to qualify for a retirement or life insurance benefit. An employee outside that scope does not become covered simply because their employment date has arrived.
Why the distinction matters
Because Article 170 separates the two coverage dates, an employer who has been operating for some time, and an employee freshly hired into that business, do not necessarily share a start date for coverage purposes. The employer's compulsory coverage has already been running since the business's first day of operation; the newly hired employee's own coverage begins on the date that particular person's employment began, which will typically come later. Someone checking whether coverage applies to a specific incident should therefore ask two separate questions — was the employer already operating, and had the employee's own employment already begun — rather than assuming a single date answers both.