diff --git a/fxprof-processed-profile/src/lib.rs b/fxprof-processed-profile/src/lib.rs
index 6bfead23..796a759c 100644
--- a/fxprof-processed-profile/src/lib.rs
+++ b/fxprof-processed-profile/src/lib.rs
@@ -91,7 +91,7 @@ pub use profile::{
     FrameHandle, FrameSymbolInfo, Profile, SamplingInterval, SourceLocation, StackHandle,
     StringHandle, TimelineUnit,
 };
-pub use reference_timestamp::ReferenceTimestamp;
+pub use reference_timestamp::{PlatformSpecificReferenceTimestamp, ReferenceTimestamp};
 pub use sample_table::WeightType;
 pub use thread::ProcessHandle;
 pub use timestamp::Timestamp;
diff --git a/fxprof-processed-profile/src/profile.rs b/fxprof-processed-profile/src/profile.rs
index dfc69589..36760ec9 100644
--- a/fxprof-processed-profile/src/profile.rs
+++ b/fxprof-processed-profile/src/profile.rs
@@ -31,7 +31,7 @@ use crate::sample_table::WeightType;
 use crate::string_table::{GlobalStringIndex, GlobalStringTable};
 use crate::thread::{ProcessHandle, Thread};
 use crate::timestamp::Timestamp;
-use crate::{FrameFlags, Symbol};
+use crate::{FrameFlags, PlatformSpecificReferenceTimestamp, Symbol};
 
 /// The sampling interval used during profile recording.
 ///
@@ -181,6 +181,7 @@ pub struct Profile {
     pub(crate) initial_visible_threads: Vec<ThreadHandle>,
     pub(crate) initial_selected_threads: Vec<ThreadHandle>,
     pub(crate) reference_timestamp: ReferenceTimestamp,
+    pub(crate) platform_specific_reference_timestamp: Option<PlatformSpecificReferenceTimestamp>,
     pub(crate) string_table: GlobalStringTable,
     pub(crate) marker_schemas: Vec<InternalMarkerSchema>,
     static_schema_marker_types: FastHashMap<&'static str, MarkerTypeHandle>,
@@ -214,6 +215,7 @@ impl Profile {
             global_libs: GlobalLibTable::new(),
             kernel_libs: LibMappings::new(),
             reference_timestamp,
+            platform_specific_reference_timestamp: None,
             processes: Vec::new(),
             string_table: GlobalStringTable::new(),
             marker_schemas: Vec::new(),
@@ -236,6 +238,14 @@ impl Profile {
         self.reference_timestamp = reference_timestamp;
     }
 
+    /// Set an additional reference timestamp with a platform-specific unit.
+    pub fn set_platform_specific_reference_timestamp(
+        &mut self,
+        platform_specific_reference_timestamp: PlatformSpecificReferenceTimestamp,
+    ) {
+        self.platform_specific_reference_timestamp = Some(platform_specific_reference_timestamp);
+    }
+
     /// Change the product name.
     pub fn set_product(&mut self, product: &str) {
         self.product = product.to_string();
@@ -1355,6 +1365,18 @@ impl Serialize for SerializableProfileMeta<'_> {
             }),
         )?;
         map.serialize_entry("startTime", &self.0.reference_timestamp)?;
+        match &self.0.platform_specific_reference_timestamp {
+            Some(PlatformSpecificReferenceTimestamp::ClockMonotonicNanosecondsSinceBoot(val)) => {
+                map.serialize_entry("startTimeAsClockMonotonicNanosecondsSinceBoot", &val)?;
+            }
+            Some(PlatformSpecificReferenceTimestamp::MachAbsoluteTimeNanoseconds(val)) => {
+                map.serialize_entry("startTimeAsMachAbsoluteTimeNanoseconds", &val)?;
+            }
+            Some(PlatformSpecificReferenceTimestamp::QueryPerformanceCounterValue(val)) => {
+                map.serialize_entry("startTimeAsQueryPerformanceCounterValue", &val)?;
+            }
+            None => {}
+        }
         map.serialize_entry("symbolicated", &self.0.symbolicated)?;
         map.serialize_entry("pausedRanges", &[] as &[()])?;
         map.serialize_entry("version", &24)?; // this version is ignored, only "preprocessedProfileVersion" is used
diff --git a/fxprof-processed-profile/src/reference_timestamp.rs b/fxprof-processed-profile/src/reference_timestamp.rs
index 1850baa5..cc2080a6 100644
--- a/fxprof-processed-profile/src/reference_timestamp.rs
+++ b/fxprof-processed-profile/src/reference_timestamp.rs
@@ -42,3 +42,12 @@ impl Serialize for ReferenceTimestamp {
         self.ms_since_unix_epoch.serialize(serializer)
     }
 }
+
+/// An additional reference timestamp in a platform-specific unit.
+#[derive(Debug, Clone, Copy, PartialEq, Eq)]
+#[non_exhaustive]
+pub enum PlatformSpecificReferenceTimestamp {
+    ClockMonotonicNanosecondsSinceBoot(u64),
+    MachAbsoluteTimeNanoseconds(u64),
+    QueryPerformanceCounterValue(u64),
+}
diff --git a/samply/src/linux_shared/converter.rs b/samply/src/linux_shared/converter.rs
index 62526002..7b308551 100644
--- a/samply/src/linux_shared/converter.rs
+++ b/samply/src/linux_shared/converter.rs
@@ -8,9 +8,9 @@ use debugid::DebugId;
 use framehop::{ExplicitModuleSectionInfo, FrameAddress, Module, Unwinder};
 use fxprof_processed_profile::{
     Category, CategoryColor, CategoryHandle, CpuDelta, FrameFlags, LibraryHandle, LibraryInfo,
-    MarkerFieldFlags, MarkerFieldFormat, MarkerTiming, Profile, ReferenceTimestamp,
-    SamplingInterval, StaticSchemaMarker, StaticSchemaMarkerField, StringHandle, SubcategoryHandle,
-    SymbolTable, ThreadHandle,
+    MarkerFieldFlags, MarkerFieldFormat, MarkerTiming, PlatformSpecificReferenceTimestamp, Profile,
+    ReferenceTimestamp, SamplingInterval, StaticSchemaMarker, StaticSchemaMarkerField,
+    StringHandle, SubcategoryHandle, SymbolTable, ThreadHandle,
 };
 use linux_perf_data::linux_perf_event_reader::TaskWasPreempted;
 use linux_perf_data::simpleperf_dso_type::{DSO_DEX_FILE, DSO_KERNEL, DSO_KERNEL_MODULE};
@@ -164,6 +164,12 @@ where
             raw_to_ns_factor: 1,
         };
 
+        profile.set_platform_specific_reference_timestamp(
+            PlatformSpecificReferenceTimestamp::ClockMonotonicNanosecondsSinceBoot(
+                timestamp_converter.reference_raw,
+            ),
+        );
+
         let cpus = if profile_creation_props.create_per_cpu_threads {
             let start_timestamp = timestamp_converter.convert_time(first_sample_time);
             Some(Cpus::new(start_timestamp, &mut profile))