Short answer. The court decides. Article 27 of the Revised Penal Code provides that a bond to keep the peace shall be required to cover such period of time as the court may determine, unlike the other penalties in the same article, which each carry a fixed statutory duration or range.
What the law says
The bond to keep the peace shall be required to cover such period of time as the court may determine.
Revised Penal Code, Article 27 — Duration Of Penalties. Read the full provision →
What the law says
The duration of the penalty of arresto menor shall be from one day to thirty days.
Revised Penal Code, Article 27 — Duration Of Penalties. Read the full provision →
No fixed period, the court decides
Article 27 states plainly that the bond to keep the peace shall be required to cover such period of time as the court may determine. There is no minimum or maximum period fixed by the statute itself, unlike the other durations the same article lays out for actual penalties of imprisonment. The length of the bond is left entirely to the court's own determination in the specific case.
How this compares to the article's other durations
The rest of Article 27 sets specific, fixed ranges: reclusion temporal runs from twelve years and one day to twenty years; prision mayor and temporary disqualification from six years and one day to twelve years; prision correccional, suspension, and destierro from six months and one day to six years; arresto mayor from one month and one day to six months; and arresto menor from one day to thirty days. The bond to keep the peace stands apart from all of these as the one duration the article leaves undefined by statute.
Why the bond is treated differently
A bond to keep the peace is not a term of imprisonment measured in a fixed range the way the other entries in Article 27 are — it is a security intended to guard against a specific risk of future misconduct, and how long that risk needs to be guarded against can vary considerably from case to case. Leaving the period to the court's determination lets the bond's duration be matched to the circumstances that made it necessary in the first place.
What the article does not resolve
Article 27 confirms that the court sets the period but does not itself provide guidance on what factors the court should weigh in fixing it, or what happens if the bond is later found to have run either too long or too short for the circumstances. Those questions are left to the court's discretion and to the specific facts of each case in which a bond to keep the peace is imposed.