crates/vm/src/stdlib/time.rs (1)

354-381: Fix platform-specific error message + avoid false positives for literal %%y

• The guard is compiled for Windows/AIX/Solaris (Line 365), but the message says “on Windows” (Line 367).
• contains("%y") (Line 366) will also trip on literal %%y (should be treated as a literal %y, not a directive).

-        // On Windows/AIX/Solaris, %y format with year < 1900 is not supported
+        // On Windows/AIX/Solaris, %y with year < 1900 is not supported
         #[cfg(any(windows, target_os = "aix", target_os = "solaris"))]
-        if instant.year() < 1900 && format.as_str().contains("%y") {
-            let msg = "format %y requires year >= 1900 on Windows";
+        if instant.year() < 1900 && has_strftime_directive(format.as_str(), 'y') {
+            let msg = "format %y requires year >= 1900 on this platform";
             return Err(vm.new_value_error(msg.to_owned()));
         }
+
+        #[cfg(any(windows, target_os = "aix", target_os = "solaris"))]
+        fn has_strftime_directive(fmt: &str, directive: char) -> bool {
+            // minimal scan to ignore escaped percent (%%)
+            let mut it = fmt.chars().peekable();
+            while let Some(c) = it.next() {
+                if c != '%' {
+                    continue;
+                }
+                match it.next() {
+                    Some('%') | None => continue, // literal '%'
+                    Some(d) if d == directive => return true,
+                    Some(_) => continue,
+                }
+            }
+            false
+        }

crates/vm/src/stdlib/signal.rs (1)

325-358: raise_signal: prefer errno/last_os_error-based exception on failure (and dedupe Windows valid-signal list)

libc::raise() failure currently returns new_os_error("raise_signal failed ...") (Line 351) but doesn’t include the platform error detail. Also, the Windows allowed-signal list is duplicated with valid_signals.

         let res = unsafe { libc::raise(signalnum) };
         if res != 0 {
-            return Err(vm.new_os_error(format!("raise_signal failed for signal {}", signalnum)));
+            return Err(std::io::Error::last_os_error().into_pyexception(vm));
         }

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