PR Stack (SDK Overhead Reduction)

• perf(core): SDK Overhead Reduction #5499
• perf(core): [SDK Overhead Reduction 1] Skip java.specification.version lookup on Android #5500
• perf(android): [SDK Overhead Reduction 2] Replace reflective OptionsContainer with direct subclass #5501
• perf(android): [SDK Overhead Reduction 3] Reuse SentryExecutorService for DeviceInfoUtil pre-caching #5502
• perf(android): [SDK Overhead Reduction 4] Use default timezone directly #5587
• perf(core): [SDK Overhead Reduction 5] Replace Calendar with Date in DateUtils #5589
• perf(core): [SDK Overhead Reduction 6] Reduce JsonWriter stack allocation #5591
• perf(core): [SDK Overhead Reduction 7] Lazily allocate Breadcrumb data #5598
• perf(core): [SDK Overhead Reduction 8] Reduce context serialization allocations #5599
• perf(core): [SDK Overhead Reduction 9] Lazily allocate reflection serializer state #5600
• perf(core): [SDK Overhead Reduction 10] Lazily create reflection JSON serializer #5601
• perf(core): [SDK Overhead Reduction 11] Replace ISO8601 timestamp handling #5602
• perf(core): [SDK Overhead Reduction 12] Avoid cloning Date getters #5603
• fix(core): [SDK Overhead Reduction 13] Preserve ISO8601 utility compatibility #5609

📜 Description

Replace Calendar.getInstance(TIMEZONE_UTC).getTime() with new Date() in DateUtils.getCurrentDateTime(), and replace the Calendar conversion in DateUtils.getDateTime(long) with new Date(millis).

Date stores epoch milliseconds and has no timezone state, so the returned values are unchanged. The UTC Calendar was only doing unnecessary allocation and calendar field computation before returning the same epoch millis as a Date.

Also update a stale Breadcrumb memoization comment that referenced Calendar allocation.

💡 Motivation and Context

Part of the SDK Overhead Reduction stack. DateUtils is used in hot event, breadcrumb, and session timestamp paths. Constructing Calendar for these helpers is unnecessary because no calendar fields are used. The change keeps Android/JDK compatibility and avoids introducing java.time or desugaring requirements.

💚 How did you test it?

• ./gradlew :sentry:test --tests io.sentry.DateUtilsTest — all tests pass
• ./gradlew spotlessApply apiDump — no API surface changes

📝 Checklist

• I added GH Issue ID & Linear ID
• I added tests to verify the changes.
• No new PII added or SDK only sends newly added PII if sendDefaultPII is enabled.
• I updated the docs if needed.
• I updated the wizard if needed.
• Review from the native team if needed.
• No breaking change or entry added to the changelog.
• No breaking change for hybrid SDKs or communicated to hybrid SDKs.

🔮 Next steps

More SDK overhead reduction PRs in this stack.

⚠️ Merge this PR using a merge commit (not squash). Only the collection branch is squash-merged into main.