Caducidad translates to "expiration" or "shelf life." It's a word commonly associated with products or food, not typically with emotions or relationships.
In "Te Lo Dije," Ha*Ash uses this word metaphorically to describe the end of a relationship, singing "Y no creíste la fecha de caducidad" (And you didn't believe the expiration date). This unexpected and poignant use of a common term in a romantic context makes it particularly striking and memorable.
Have you ever felt like you were talking, but no one was listening? In "Te Lo Dije," which translates to "I Told You So," the sister duo Ha*Ash sings about the end of a relationship where one person feels completely ignored and taken for granted. The singer describes a partner who comes home at night without asking about her day and leaves in the morning without even a kiss. She tried many times to explain her feelings of loneliness, but her partner always "turned their back" on her.
This song is a powerful declaration that she's done trying. She repeatedly warns her partner, "I told you so, sooner or later it was going to happen," but they never believed her. Now, she's tired of crying and has decided there's no turning back. The love has an expiration date ("la fecha de caducidad"), and that date has finally arrived. It's a classic "you'll miss me when I'm gone" anthem, ending with the confident prediction: "Me vas a extrañar" (You're going to miss me).