diff --git a/requirements/requirements-dev.txt b/requirements/requirements-dev.txt
index 98b4a58..71e17ea 100644
--- a/requirements/requirements-dev.txt
+++ b/requirements/requirements-dev.txt
@@ -26,7 +26,9 @@ pyflakes==2.1.1           # via flake8
 pyparsing==2.4.6          # via packaging
 pytest-cov==2.8.1         # via -r requirements/requirements-dev.in
 pytest==5.3.5             # via -r requirements/requirements-dev.in, pytest-cov
+pytz==2019.3              # via tzlocal
 six==1.14.0               # via packaging, pip-tools
+tzlocal==2.0.0            # via -r requirements/requirements.in
 versioneer==0.18          # via -r requirements/requirements-dev.in
 wcwidth==0.1.8            # via pytest
 werkzeug==1.0.0           # via flask
diff --git a/requirements/requirements.in b/requirements/requirements.in
index 62ad2c6..2769af8 100644
--- a/requirements/requirements.in
+++ b/requirements/requirements.in
@@ -1,2 +1,3 @@
 Flask                       # general purpose web service and web server stuff
 Markdown                    # markdown rendering in templates
+tzlocal                     # identifying system's local timezone
diff --git a/requirements/requirements.txt b/requirements/requirements.txt
index f479d9f..356c974 100644
--- a/requirements/requirements.txt
+++ b/requirements/requirements.txt
@@ -10,6 +10,8 @@ itsdangerous==1.1.0       # via flask
 jinja2==2.11.1            # via flask
 markdown==3.2.1           # via -r requirements/requirements.in
 markupsafe==1.1.1         # via jinja2
+pytz==2019.3              # via tzlocal
+tzlocal==2.0.0            # via -r requirements/requirements.in
 werkzeug==1.0.0           # via flask
 
 # The following packages are considered to be unsafe in a requirements file: