diff -ur action.d.old//sendmail.conf action.d//sendmail.conf
--- action.d.old//sendmail.conf	2012-06-10 13:23:07.000000000 +0200
+++ action.d//sendmail.conf	2012-06-10 13:23:18.000000000 +0200
@@ -12,7 +12,7 @@
 # Values:  CMD
 #
 actionstart = printf %%b "Subject: [Fail2Ban] <name>: started
-              Date: `date -u +"%%a, %%d %%h %%Y %%T +0000"`
+              Date: `LANG=C date -u +"%%a, %%d %%h %%Y %%T +0000"`
               From: Fail2Ban <<sender>>
               To: <dest>\n
               Hi,\n
@@ -25,7 +25,7 @@
 # Values:  CMD
 #
 actionstop = printf %%b "Subject: [Fail2Ban] <name>: stopped
-             Date: `date -u +"%%a, %%d %%h %%Y %%T +0000"`
+             Date: `LANG=C date -u +"%%a, %%d %%h %%Y %%T +0000"`
              From: Fail2Ban <<sender>>
              To: <dest>\n
              Hi,\n
@@ -48,7 +48,7 @@
 # Values:  CMD
 #
 actionban = printf %%b "Subject: [Fail2Ban] <name>: banned <ip>
-            Date: `date -u +"%%a, %%d %%h %%Y %%T +0000"`
+            Date: `LANG=C date -u +"%%a, %%d %%h %%Y %%T +0000"`
             From: Fail2Ban <<sender>>
             To: <dest>\n
             Hi,\n
diff -ur action.d.old//sendmail-whois.conf action.d//sendmail-whois.conf
--- action.d.old//sendmail-whois.conf	2012-06-10 13:21:29.000000000 +0200
+++ action.d//sendmail-whois.conf	2012-06-10 13:22:42.000000000 +0200
@@ -12,7 +12,7 @@
 # Values:  CMD
 #
 actionstart = printf %%b "Subject: [Fail2Ban] <name>: started
-              Date: `date -u +"%%a, %%d %%h %%Y %%T +0000"`
+              Date: `LANG=C date -u +"%%a, %%d %%h %%Y %%T +0000"`
               From: Fail2Ban <<sender>>
               To: <dest>\n
               Hi,\n
@@ -25,7 +25,7 @@
 # Values:  CMD
 #
 actionstop = printf %%b "Subject: [Fail2Ban] <name>: stopped
-             Date: `date -u +"%%a, %%d %%h %%Y %%T +0000"`
+             Date: `LANG=C date -u +"%%a, %%d %%h %%Y %%T +0000"`
              From: Fail2Ban <<sender>>
              To: <dest>\n
              Hi,\n
@@ -48,7 +48,7 @@
 # Values:  CMD
 #
 actionban = printf %%b "Subject: [Fail2Ban] <name>: banned <ip>
-            Date: `date -u +"%%a, %%d %%h %%Y %%T +0000"`
+            Date: `LANG=C date -u +"%%a, %%d %%h %%Y %%T +0000"`
             From: Fail2Ban <<sender>>
             To: <dest>\n
             Hi,\n
diff -ur action.d.old//sendmail-whois-lines.conf action.d//sendmail-whois-lines.conf
--- action.d.old//sendmail-whois-lines.conf	2012-06-10 13:25:52.000000000 +0200
+++ action.d//sendmail-whois-lines.conf	2012-06-10 13:26:06.000000000 +0200
@@ -12,7 +12,7 @@
 # Values:  CMD
 #
 actionstart = printf %%b "Subject: [Fail2Ban] <name>: started
-              Date: `date -u +"%%a, %%d %%h %%Y %%T +0000"`
+              Date: `LANG=C date -u +"%%a, %%d %%h %%Y %%T +0000"`
               From: Fail2Ban <<sender>>
               To: <dest>\n
               Hi,\n
@@ -25,7 +25,7 @@
 # Values:  CMD
 #
 actionstop = printf %%b "Subject: [Fail2Ban] <name>: stopped
-             Date: `date -u +"%%a, %%d %%h %%Y %%T +0000"`
+             Date: `LANG=C date -u +"%%a, %%d %%h %%Y %%T +0000"`
              From: Fail2Ban <<sender>>
              To: <dest>\n
              Hi,\n
@@ -48,7 +48,7 @@
 # Values:  CMD
 #
 actionban = printf %%b "Subject: [Fail2Ban] <name>: banned <ip>
-            Date: `date -u +"%%a, %%d %%h %%Y %%T +0000"`
+            Date: `LANG=C date -u +"%%a, %%d %%h %%Y %%T +0000"`
             From: Fail2Ban <<sender>>
             To: <dest>\n
             Hi,\n