Patch submitted upstream: https://github.com/robotframework/robotframework/pull/4286.

diff --git a/atest/robot/standard_libraries/operating_system/modified_time.robot b/atest/robot/standard_libraries/operating_system/modified_time.robot
index d144ffd34..c7681e61d 100644
--- a/atest/robot/standard_libraries/operating_system/modified_time.robot
+++ b/atest/robot/standard_libraries/operating_system/modified_time.robot
@@ -8,7 +8,7 @@ ${TESTFILE}       %{TEMPDIR}${/}robot-os-tests${/}f1.txt
 *** Test Cases ***
 Get Modified Time As Timestamp
     ${tc} =    Check Test Case    ${TESTNAME}
-    Should Match Regexp    ${tc.kws[0].msgs[0].message}    Last modified time of '<a href=.*</a>' is 20\\d\\d-\\d\\d-\\d\\d \\d\\d:\\d\\d:\\d\\d
+    Should Match Regexp    ${tc.kws[0].msgs[0].message}    Last modified time of '<a href=.*</a>' is \\d\\d\\d\\d-\\d\\d-\\d\\d \\d\\d:\\d\\d:\\d\\d
 
 Get Modified Time As Seconds After Epoch
     ${tc} =    Check Test Case    ${TESTNAME}
diff --git a/atest/testdata/standard_libraries/builtin/get_time.robot b/atest/testdata/standard_libraries/builtin/get_time.robot
index 9847d8c42..24ce732ca 100644
--- a/atest/testdata/standard_libraries/builtin/get_time.robot
+++ b/atest/testdata/standard_libraries/builtin/get_time.robot
@@ -11,18 +11,18 @@ Get Time As Timestamp
 
 Get Time As Seconds After Epoch
     ${time} =    Get Time    epoch
-    Should Be True    1000000000 < ${time} < 2000000000
+    Should Be True    0 < ${time}
 
 Get Time As Parts
     @{time} =    Get Time    year, month, day, hour, min, sec
-    Should Be True    2000 < ${time}[0] < 2100
+    Should Match Regexp    ${time}[0]    \\d{4}
     Should Be True    1 <= int('${time}[1]') <= 12
     Should Be True    1 <= int('${time}[2]') <= 31
     Should Be True    0 <= int('${time}[3]') <= 23
     Should Be True    0 <= int('${time}[4]') <= 59
     Should Be True    0 <= int('${time}[5]') <= 59
     ${year}    ${min}    ${sec} =    Get Time    seconds and minutes and year and whatnot
-    Should Be True    2000 < ${year} < 2100
+    Should Match Regexp    ${year}    \\d{4}
     Should Be True    0 <= int('${min}') <= 59
     Should Be True    0 <= int('${sec}') <= 59
 
diff --git a/atest/testdata/standard_libraries/operating_system/modified_time.robot b/atest/testdata/standard_libraries/operating_system/modified_time.robot
index 9489b3c9c..c712ebaed 100644
--- a/atest/testdata/standard_libraries/operating_system/modified_time.robot
+++ b/atest/testdata/standard_libraries/operating_system/modified_time.robot
@@ -14,13 +14,13 @@ Get Modified Time As Timestamp
 
 Get Modified Time As Seconds After Epoch
     ${dirtime} =    Get Modified Time    ${CURDIR}    epoch
-    Should Be True    1000000000 < ${dirtime} < 2000000000
+    Should Be True    ${dirtime} > 0
     ${current} =    Get Time    epoch
     Should Be True    ${current} >= ${dirtime}
 
 Get Modified Time As Parts
     ${year} =    Get Modified Time    ${CURDIR}    year
-    Should Be True    2000 < ${year} < 2100
+    Should Match Regexp    ${year}    \\d{4}
     ${yyyy}    ${mm}    ${dd} =    Get Modified Time    ${CURDIR}    year, month, day
     Should Be Equal    ${yyyy}    ${year}
     # Must use `int('x')` because otherwise 08 and 09 are considered octal
'msg-avail'>...<span class='msg-tooltip'>* gnu/packages/stb.scm (stb): Update to commit b42009b3b9d4ca35bc703f5310eedc74f584be58..
(stb-image): Update version number to 2.26.
(stb-image-write): Update version number to 1.15.
(stb-sprintf): Update version number to 1.09.
(stb-truetype): Update version number to 1.24.
</span></span></td><td>Tobias Geerinckx-Rice</td></tr>
<tr><td><span title='2020-11-15 00:12:11 +0100'>2020-11-15</span></td><td><a href='/guix/commit/gnu/packages/stb.scm?id=6f5f60b2891b15036375be28ace1ca87e250d667'>gnu: Add stb-rect-pack.</a><span class='msg-avail'>...<span class='msg-tooltip'>* gnu/packages/stb.scm (stb-rect-pack): New public variable.
</span></span></td><td>Tobias Geerinckx-Rice</td></tr>