dmesg: set to fixed timezone in test.

src/uu/dmesg/src/dmesg.rs

@@ -108,25 +108,11 @@ pub fn uumain(args: impl uucore::Args) -> UResult<()> {
     }
     if let Some(since) = matches.get_one::<String>(options::SINCE) {
         let since = remove_enclosing_quotes(since);
-        if let Ok(since) = parse_datetime::parse_datetime(since) {
-            dmesg.since_filter = Some(since);
-        } else {
-            return Err(USimpleError::new(
-                1,
-                format!("invalid time value \"{since}\""),
-            ));
-        }
+        dmesg.since_filter = Some(time_formatter::parse_datetime(since)?);
     }
     if let Some(until) = matches.get_one::<String>(options::UNTIL) {
         let until = remove_enclosing_quotes(until);
-        if let Ok(until) = parse_datetime::parse_datetime(until) {
-            dmesg.until_filter = Some(until);
-        } else {
-            return Err(USimpleError::new(
-                1,
-                format!("invalid time value \"{until}\""),
-            ));
-        }
+        dmesg.until_filter = Some(time_formatter::parse_datetime(until)?);
     }
     dmesg.print()?;
     Ok(())

src/uu/dmesg/src/time_formatter.rs

@@ -7,6 +7,7 @@ use chrono::{DateTime, FixedOffset, TimeDelta};
 #[cfg(feature = "fixed-boot-time")]
 use chrono::{NaiveDate, NaiveTime};
 use std::sync::OnceLock;
+use uucore::error::{UResult, USimpleError};
 
 pub fn raw(timestamp_us: i64) -> String {
     let seconds = timestamp_us / 1000000;
@@ -116,6 +117,15 @@ impl DeltaFormatter {
     }
 }
 
+pub fn parse_datetime(s: &str) -> UResult<DateTime<FixedOffset>> {
+    #[cfg(feature = "fixed-boot-time")]
+    set_fixed_timezone();
+    match parse_datetime::parse_datetime(s) {
+        Ok(date_time) => Ok(date_time),
+        Err(_) => Err(USimpleError::new(1, format!("invalid time value \"{s}\""))),
+    }
+}
+
 pub fn datetime_from_microseconds_since_boot(microseconds: i64) -> DateTime<FixedOffset> {
     boot_time()
         .checked_add_signed(TimeDelta::microseconds(microseconds))
@@ -174,3 +184,11 @@ fn boot_time_from_utmpx() -> Option<DateTime<FixedOffset>> {
     }
     None
 }
+
+#[cfg(feature = "fixed-boot-time")]
+static SET_TZ: OnceLock<()> = OnceLock::new();
+
+#[cfg(feature = "fixed-boot-time")]
+fn set_fixed_timezone() {
+    *SET_TZ.get_or_init(|| std::env::set_var("TZ", "Asia/Jakarta"))
+}