Version 3.0.1 of a REST API implementation represents time values in PST time using ISO 8601 hh:mm:ss format. The API implementation needs to be…

Changing the timezone of a data field (from PST to CEST) in an API response is a backward-incompatible or "breaking" change. Any client application built to consume version 3.0.1 would have logic assuming the PST timezone. When the API starts sending CEST times, this client logic will fail or produce incorrect results.

The Semantic Versioning 2.0.0 specification, which the question requires following, explicitly states that the MAJOR version must be incremented for any backward-incompatible changes. Incrementing the MAJOR version from 3 to 4 and resetting the MINOR and PATCH versions to 0 results in the new version 4.0.0.

A. 3.0.2: This indicates a PATCH release, which is strictly for backward-compatible bug fixes. This change is a modification of the data contract, not a bug fix.

C. 3.1.0: This indicates a MINOR release, which is for adding new functionality in a backward-compatible manner. This change modifies existing functionality incompatibly.

D. 3.0.1: This is the current version. Since a change is being made to the API implementation, a new version number must be assigned.

1. Semantic Versioning 2.0.0 Specification:

Source: semver.org

Reference: Summary, Item 8: "Major version X (X.y.z | X > 0) MUST be incremented if any backwards incompatible changes are introduced to the public API. It MAY include minor and patch level changes. Patch and minor version MUST be reset to 0 when major version is incremented." This directly supports that a breaking change requires a major version increment.

2. MuleSoft Anypoint Platform Documentation, API Manager:

Source: MuleSoft Documentation

Reference: Section: "Versioning an API". The documentation states, "A major version change (for example, v1 to v2) indicates that you have made breaking changes to your API. A breaking change is a change that is not backward-compatible with previous versions." This aligns the MuleSoft best practice with the semver.org standard.