1. What is Date/Time Fingerprinting
Date/Time fingerprinting refers to the techniques that websites use to extract and analyze localized time-related values from the browser, primarily by inspecting the Date object and its output in various contexts. For example, output from:
new Date().toString()new Date().toISOString()Intl.DateTimeFormat().resolvedOptions()Date.now()performance.now()
These functions expose critical user data such as:
- Local time vs UTC
- Timezone offset
- Daylight-saving behavior
- Locale-based time formatting
While the actual time is dynamic, the pattern and format how JavaScript routines return time data are consistent across users from the same region or timezone — turning them into fingerprintable signals.
2. How Websites Exploit Date/Time Fingerprints
Advanced tracking systems and fingerprint engines use the time data to:
- Detect timezone offsets: Comparing localized time strings and their offset to UTC can help determine the user’s geographic position.
- Check Local Time Validity: Sites can validate if a user’s time aligns with their claimed location, helping to reject sessions from inconsistent environments.
- Timezone-based Fingerprint Hashing: Timezone info combined with current screen time, region format, and daylight saving date logic allows platforms to build distinguishing hashes.
- Compare with Server Time: Timing differences or unusual date formatting may be used as soft red flags to determine if a session is simulated, automated, or out-of-context.
- Consistency Checks in Multi-Accounting: Platforms compare how different accounts respond to identical date/time test requests. If results overlap, it can trigger anti-fraud logic.
In such scenarios, even a few seconds of drift or a mismatched timezone label (Europe/Paris vs "Asia/Shanghai") can reveal that profiles are running on the same machine, undermining account isolation efforts.
3. How FlashID Manipulates and Protects Date/Time Fingerprints
FlashID ensures each browser profile outputs plausible and consistent time values, precisely aligned with the rest of the spoofed fingerprint (timezone, language, IP location) to evade association systems.
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