It's a common misconception that all contracts become enforceable the day they are signed. However, this is not always true. In many circumstances, the execution date of a contract occurs before the effective date.
Effective date versus execution date
The effective date is when your obligations outlined in the contract begin. In other words, contracts become enforceable on the effective date. This date cannot precede the execution date, meaning a contract cannot be in effect until after all parties sign it.
Sometimes an effective date is a fixed date that is explicitly stated. However, the contract might not begin on a fixed date and may be conditional instead. If a contract begins on the date all parties sign it, that is a conditional effective date.
The execution date is the day both parties have signed the contract. It's when both parties agree to the contract's terms and conditions. However, this isn't necessarily the same day the contract comes into effect.
For example, if you're moving into a new apartment, you may sign your Residential Lease in advance. Though you may sign the lease well before you officially move into your new rental property, you are not bound by the terms of your lease until after the effective date.
This means even if you signed your lease months before moving in, you're not obligated to keep the unit clean, pay rent, or anything else until your lease actually begins (unless something in your contract specifies otherwise). Conversely, you are also not allowed to live on the premises until the effective date.
Keep in mind that a contract isn't valid until all the necessary parties sign it—regardless of its effective date.