By default, Internet Information Services (IIS) uses the W3C Extended Log File Format. This standard specifies that all log entries must use Coordinated Universal Time (UTC) for their timestamps. This practice ensures consistency and avoids ambiguity when analyzing logs from servers located in different geographical time zones or when accounting for Daylight Saving Time changes. The screenshot displays a standard W3C log format, and since the question specifies a default installation, the time standard is UTC.

B. GMT: While colloquially used interchangeably with UTC, GMT is an older time standard based on solar time. UTC is the modern, precise atomic time standard specified for W3C logging.
C. TAI: International Atomic Time (TAI) is the basis for UTC but does not include leap seconds. Server logs and network time protocols use UTC, not TAI directly.
D. UT: Universal Time (UT) is a time standard based on the Earth's rotation. UTC is the globally accepted standard for computer systems and is synchronized with, but distinct from, UT.

1. Microsoft Corporation. (2007). IIS 6.0 Operations Guide. TechNet. In Chapter 11: Analyzing Log Files, the section "Reading Log Files" states, "The time is recorded as Coordinated Universal Time (UTC)."

2. Microsoft Support. (2017, January 12). KB271196: The time in the IIS log files is not correct. "By default, Internet Information Services (IIS) uses Coordinated Universal Time (UTC), formerly known as Greenwich Mean Time (GMT), for logging."

3. University of Washington, IT Connect. (n.d.). Understanding IIS Log Files. "By default, IIS logs events in UTC (Coordinated Universal Time) time. This is the recommended setting because it will not be affected by changes in the server's time zone or by daylight savings time."

4. Fielding, R., & Reschke, J. (2014). Hypertext Transfer Protocol (HTTP/1.1): Semantics and Content. RFC 7231. Section 7.1.1.1, "Date/Time Formats," specifies the use of Greenwich Mean Time (GMT) as the reference for HTTP date formats, which is the predecessor standard to UTC for this context. Modern implementations, including W3C logging for servers like IIS, have standardized on the more precise UTC.