diff --git a/CHANGELOG.md b/CHANGELOG.md
index 1fb1fa15..950956d4 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -10,6 +10,7 @@ The full list of changes can be found in the compare view for the respective rel
 
 - profiles: clarify Sample message usage guidance docs. [#742](https://github.com/open-telemetry/opentelemetry-proto/pull/742)
 - profiles: improve Sample message clarity and usage documentation. [#724](https://github.com/open-telemetry/opentelemetry-proto/pull/724)
+- profiles: clarify the profile and sample timestamps relationship. [#744](https://github.com/open-telemetry/opentelemetry-proto/pull/744)
 
 ### Fixed
 
diff --git a/opentelemetry/proto/profiles/v1development/profiles.proto b/opentelemetry/proto/profiles/v1development/profiles.proto
index 1779bbd5..fede0cf3 100644
--- a/opentelemetry/proto/profiles/v1development/profiles.proto
+++ b/opentelemetry/proto/profiles/v1development/profiles.proto
@@ -284,9 +284,14 @@ message Profile {
   // The following fields 3-12 are informational, do not affect
   // interpretation of results.
 
-  // Time of collection (UTC) represented as nanoseconds past the epoch.
+  // Time of collection. Value is UNIX Epoch time in nanoseconds since 00:00:00
+  // UTC on 1 January 1970.
   fixed64 time_unix_nano = 3;
-  // Duration of the profile, if a duration makes sense.
+  // Duration of the profile. For instant profiles like live heap snapshot, the
+  // duration can be zero but it may be preferable to set time_unix_nano to the
+  // process start time and duration_nano to the relative time when the profile
+  // was gathered. This ensures Sample.timestamps_unix_nano values such as
+  // allocation timestamp fall into the profile time range.
   uint64 duration_nano = 4;
   // The kind of events between sampled occurrences.
   // e.g [ "cpu","cycles" ] or [ "heap","bytes" ]
@@ -401,8 +406,10 @@ message Sample {
 
   // The type and unit of each value is defined by Profile.sample_type.
   repeated int64 values = 4;
-  // Timestamps associated with Sample represented in nanoseconds. These
-  // timestamps should fall within the Profile's time range.
+  // Timestamps associated with Sample. Value is UNIX Epoch time in nanoseconds
+  // since 00:00:00 UTC on 1 January 1970. The timestamps should fall within the
+  // [Profile.time_unix_nano, Profile.time_unix_nano + Profile.duration_nano)
+  // time range.
   repeated fixed64 timestamps_unix_nano = 5;
 }