If possible, move to a modern Windows version that natively supports the precise API.
GetSystemTimePreciseAsFileTime is a Windows API that returns the current system time with the highest-resolution clock available, in FILETIME (100-nanosecond) units. It was introduced in Windows 8 and is not present in stock Windows 7 API surface. However, some patched or updated Windows 7 systems can expose it via updates or compatibility shims.
Below is concise, practical content you can use (documentation-style + code examples, detection and fallback guidance, and notes about risks and compatibility).
To understand the patch, you must first understand the target.
GetSystemTimePreciseAsFileTime (defined in sysinfoapi.h) retrieves the current system date and time in a single FILETIME structure (a 64-bit value counting 100-nanosecond intervals since January 1, 1601 UTC). The “Precise” in its name is the kicker: it returns the most accurate system time-of-day available, often incorporating the high-resolution performance counter to interpolate between system clock ticks. getsystemtimepreciseasfiletime windows 7 patched
In practice:
Some system-level patches (often for specific applications like game servers or databases) install a kernel shim. This requires loading a signed (or test-signed) driver that modifies the System Service Dispatch Table (SSDT) to redirect the system call originating from GetSystemTimePreciseAsFileTime. This is risky, triggers PatchGuard (Kernel Patch Protection) on 64-bit Windows 7, and is generally not recommended for production systems.
Subject: System Time Precision, API Back-porting, and Kernel32.dll Updates Target Environment: Windows 7 (Pre- and Post-Windows 8 Release)
While Microsoft did not expose the combined high-precision API in Windows 7 user-mode libraries, the underlying kernel capability was there all along. If possible, move to a modern Windows version
Enter NtQuerySystemTime.
This is a native API function found in ntdll.dll. While ntdll functions are technically undocumented, NtQuerySystemTime has been known to the reverse engineering community for decades.
Unlike GetSystemTimeAsFileTime, which reads a cached value updated by the system clock interrupt, NtQuerySystemTime reads the time directly from the system’s time structures. On Windows 7 (specifically versions that support the SharedUserData system clock update logic), this function returns the high-resolution system time—effectively behaving exactly like the GetSystemTimePreciseAsFileTime that appeared in Windows 8.
Windows 7’s kernel (ntoskrnl.exe) and its time management architecture were designed before the demand for sub-millisecond system time-of-day became mainstream. The system’s default timer resolution is 15.6 milliseconds (64 Hz). While you could adjust this using timeBeginPeriod(1) to get 1 ms resolution, GetSystemTimeAsFileTime would still only update at that resolution, leading to “stepped” time. However, some patched or updated Windows 7 systems
Microsoft made a conscious decision: backporting GetSystemTimePreciseAsFileTime to Windows 7 would require significant changes to the kernel’s time interpolation logic. Additionally, the function relies on newer HAL (Hardware Abstraction Layer) features for continuous timestamp calibration. Since Windows 7 exited mainstream support in 2015 (extended support until 2020, but no new features), Microsoft never officially released it.
This left developers with an ugly choice on Windows 7:
Microsoft no longer supports Windows 7 (EOL January 2020). However, some enterprises pay for ESU (Extended Security Updates). A patched DLL could break after a security update.