Short answer. Only the hours after 10pm. Article 86 of the Labor Code entitles every employee to a night shift differential of not less than 10% of their regular wage for each hour worked between ten o'clock in the evening and six o'clock in the morning — hours before 10pm are not covered by this differential.
What the law says
Every employee shall be paid a night shift differential of not less than ten percent (10%) of his regular wage for each hour of work performed between ten o’clock in the evening and six o’clock in the morning.
Labor Code, Article 86 — Night Shift Differential. Read the full provision →
The window is fixed by the statute
Article 86 defines the covered period precisely: between ten o'clock in the evening and six o'clock in the morning. That is the window the night shift differential attaches to, and it does not shift based on when your particular shift happens to start. An 8pm shift means two hours — 8pm to 10pm — fall outside that window, and the differential applies only to the hours actually worked from 10pm onward within your shift.
It is calculated hour by hour
The differential is expressed for each hour of work performed within the window, not as a flat bonus that applies to an entire shift once any part of it touches the covered hours. That phrasing means the calculation should track exactly how many hours of your shift actually fall between 10pm and 6am, and apply the differential to that portion — the hours before 10pm are paid at your regular rate, with no night differential attached to them.
What the rate itself guarantees
For every hour that does fall in the covered window, Article 86 sets a floor: not less than ten percent (10%) of your regular wage, added on top for that hour. An employer can pay more than 10%, but not less, for hours actually worked in that period. This is a minimum standard the statute sets directly, rather than something left to be negotiated away in your employment contract.
Checking your own payslip against this
If your shift straddles the 10pm line, look at your payslip to see whether the differential is being computed only on the hours after 10pm, or is missing entirely. Keeping a record of your actual clock-in and clock-out times is the most direct way to confirm whether you are being paid correctly for the night hours you work, and it is the evidence you would need if you ever had to raise a shortfall with your employer or the labor authorities.