diff --git a/docs/parsers/vmstat.md b/docs/parsers/vmstat.md
index a627f427..c220728c 100644
--- a/docs/parsers/vmstat.md
+++ b/docs/parsers/vmstat.md
@@ -5,6 +5,10 @@ jc - JSON CLI output utility `vmstat` command output parser
 
 Options supported: `-a`, `-w`, `-d`, `-t`
 
+The `epoch` calculated timestamp field is naive (i.e. based on the local time of the system the parser is run on)
+
+The `epoch_utc` calculated timestamp field is timezone-aware and is only available if the timezone field is UTC.
+
 Usage (cli):
 
     $ vmstat | jc --vmstat
diff --git a/docs/parsers/vmstat_s.md b/docs/parsers/vmstat_s.md
index 77c2463b..09c93df5 100644
--- a/docs/parsers/vmstat_s.md
+++ b/docs/parsers/vmstat_s.md
@@ -5,6 +5,10 @@ jc - JSON CLI output utility `vmstat` command output streaming parser
 
 Options supported: `-a`, `-w`, `-d`, `-t`
 
+The `epoch` calculated timestamp field is naive (i.e. based on the local time of the system the parser is run on)
+
+The `epoch_utc` calculated timestamp field is timezone-aware and is only available if the timezone field is UTC.
+
 Usage (cli):
 
     $ vmstat | jc --vmstat-s
diff --git a/jc/parsers/vmstat.py b/jc/parsers/vmstat.py
index f4f75815..65a3e29c 100644
--- a/jc/parsers/vmstat.py
+++ b/jc/parsers/vmstat.py
@@ -2,6 +2,10 @@
 
 Options supported: `-a`, `-w`, `-d`, `-t`
 
+The `epoch` calculated timestamp field is naive (i.e. based on the local time of the system the parser is run on)
+
+The `epoch_utc` calculated timestamp field is timezone-aware and is only available if the timezone field is UTC.
+
 Usage (cli):
 
     $ vmstat | jc --vmstat
diff --git a/jc/parsers/vmstat_s.py b/jc/parsers/vmstat_s.py
index eea42362..9600a6f7 100644
--- a/jc/parsers/vmstat_s.py
+++ b/jc/parsers/vmstat_s.py
@@ -2,6 +2,10 @@
 
 Options supported: `-a`, `-w`, `-d`, `-t`
 
+The `epoch` calculated timestamp field is naive (i.e. based on the local time of the system the parser is run on)
+
+The `epoch_utc` calculated timestamp field is timezone-aware and is only available if the timezone field is UTC.
+
 Usage (cli):
 
     $ vmstat | jc --vmstat-s