Electronic timestamp: what it is, how it works, and why to integrate it via API into your digital processes

Time stamps are the tool that allows an electronic document to be associated with a certain date and time, guaranteed by a third party and enforceable against third parties in legal contexts.

Very often, in fact, the validity of a file does not depend only on who signed it, but also on indisputable proof of when the action took place and on the guarantee that the document has not been altered after that moment.

The electronic timestamp is what gives full legal value to the document, protecting its integrity over time and making it, in all respects, a secure and indisputable digital asset.

Timestamp: what it is and what it is used for

An electronic timestamp, or time stamp, is a sequence of characters that uniquely associates a certain date and time with a specific file.

Within the eIDAS 2.0 Regulation, electronic time validation is defined as:

“Data in electronic form which binds other electronic data to a particular time and date, thereby establishing that the latter data existed at that time and date.”

Like the postmark of registered mail, a timestamp proves that a document existed at a specific moment. However, time stamping offers a much higher level of security than a simple stamp, not only because it certifies the time of marking with far greater precision, but also because it guarantees the integrity of the file, ensuring that it has not been modified after its time validation.

What is the difference between a timestamp and a time reference?

In general, a time reference is a generic association between a document and a certain date and time. In practice, however, when referring to the time reference of a digital document, it usually means time stamping, which is the primary tool for associating a file with a specific moment in an indisputable way.

The key difference between a generic time reference, managed by the user, and the time validation of an electronic document lies in its enforceability against third parties. According to eIDAS, a qualified timestamp “freezes” the integrity of the document by linking it to a certain date and time, whose reliability is guaranteed by the fact that the timestamp is issued by a Qualified Trust Service Provider (Time Stamping Authority) accredited by AgID.

What does qualified time stamping mean?

The requirements for qualified electronic time validation are outlined in Article 42 of the eIDAS Regulation. In addition to ensuring the immutability of the document, it must be based on an accurate time source linked to Coordinated Universal Time. Even more importantly, it must be “created using an advanced electronic signature or sealed with an advanced electronic seal of the qualified trust service provider.”

The full legal value of the timestamp is therefore guaranteed by the presence of an accredited third-party certification authority which, acting as a digital notary, ensures its authenticity and integrity at a European level.

With eIDAS 2.0, timestamping must meet even higher security requirements, in line with the NIS 2 Directive. It has also become a native tool for the European Digital Identity Wallet (EUDI): all EU Member States are required to recognize a qualified timestamp issued by a provider from another Member State.

How does the time stamping process work?

When deciding to apply a timestamp to an electronic invoice, a VAT register, or a digital artwork, the signing software (or the application using timestamping APIs) calculates the document hash, assigning it a unique string that identifies it.

This hash — and not the entire document, which remains confidential — is then sent to the server of the Qualified Trust Service Provider in an operation known as a Time Stamping Authority (TSA) request.

The provider’s server receives the hash and applies two fundamental elements: a certain date and time from certified UTC-synchronized sources, and an electronic seal, which acts as the digital signature of the package consisting of the hash and timestamp. At that point, the TSA returns the actual timestamp, which can be embedded directly into the file (for example, a PDF) or stored as a separate file (usually with a .tsr extension) alongside the digital document.

Why integrate time stamping via API

Many companies purchase timestamp packages to validate their documents: in this case, time stamping is typically performed manually, using desktop software or applications. However, when dealing with very high volumes of documents, manual stamping quickly reveals its limitations.

In such cases, the only truly efficient solution is API integration, which ensures:

• Automation: by integrating timestamping APIs directly into your management system, CRM, or ERP, the process can be automated, allowing invoices, contracts, and system logs to be timestamped the moment they are created, without any human intervention;
• Scalability: by removing the human factor and enabling hundreds of simultaneous requests, workflow bottlenecks are eliminated;
• Compliance: by integrating the timestamping APIs of a qualified provider, regulatory compliance becomes a native feature of the software;
• Traceability and monitoring: unlike manual stamping, API calls allow real-time monitoring of usage and provide detailed logs for each operation.

In essence, moving from manual management to an API-based infrastructure makes it possible to transform a compliance requirement into a strategic operational advantage, secure and fully integrated into existing workflows.