Short answer. Yes, generally. Article 2253 says a right declared for the first time in the Civil Code is effective at once, even if the act or event giving rise to it happened under the old law, provided the new right does not prejudice or impair any vested right of the same origin.
What the law says
But if a right should be declared for the first time in this Code, it shall be effective at once, even though the act or event which gives rise thereto may have been done or may have occurred under prior legislation, provided said new right does not prejudice or impair any vested or acquired right, of the same origin.
Civil Code, Article 2253 — Old Law Governs Prior Acts. Read the full provision →
What the law says
The Civil Code of 1889 and other previous laws shall govern rights originating, under said laws, from acts done or events which took place under their regime, even though this Code may regulate them in a different manner, or may not recognize them.
Civil Code, Article 2253 — Old Law Governs Prior Acts. Read the full provision →
A newly declared right applies immediately
Article 2253 answers your question with a clear rule favoring immediate application: "if a right should be declared for the first time in this Code, it shall be effective at once, even though the act or event which gives rise thereto may have been done or may have occurred under prior legislation." A right that simply did not exist before the new Code created it is not held back by the fact that the underlying act or event happened while the old law was still in force.
The important limitation built into the rule
This immediate effect is not unconditional. The article adds the qualifier that the new right applies "provided said new right does not prejudice or impair any vested or acquired right, of the same origin." If someone else already holds a vested right arising from that same act or event under the old law, your ability to claim the newly declared right cannot be used to defeat or diminish what that other person already validly acquired.
How this fits with the Code's general approach to prior acts
This rule operates alongside the more general transitional principle that "the Civil Code of 1889 and other previous laws shall govern rights originating, under said laws, from acts done or events which took place under their regime, even though this Code may regulate them in a different manner, or may not recognize them." The general rule keeps the old law in charge of rights that already existed under it; the exception for newly declared rights lets genuinely new entitlements apply immediately, precisely because there was no old right in that specific respect for the old law to protect.
What this means for your situation
If the right you want to claim genuinely did not exist before the Civil Code created it, Article 2253 supports claiming it now even though the underlying act or event took place under the old law. The remaining question is whether granting you that new right would prejudice or impair some other person's already-vested right arising from the very same act or event — if it would, that vested right takes precedence, and the new right cannot be used to override it.