diff --git a/README.md b/README.md
index f76f549..d073a3e 100644
--- a/README.md
+++ b/README.md
@@ -14,5 +14,14 @@ but a brief overview of the components:
 * Cutter interacts with a database to perform cutting jobs
 * Sheet Sync syncs specifc database columns to a google doc which is the primary operator interface.
 
+### Usage
+
 All components are built as docker images.
 Components which access the disk expect a shared directory mounted at `/mnt`.
+
+#### Configuration
+
+Configuration is built into the docker images, and set during build by specifying a
+YAML file `config.yaml` in the repository root directory.
+
+See the provided example file for documentation of options.
diff --git a/common/common.py b/common/common.py
index 7c2a23a..94b337e 100644
--- a/common/common.py
+++ b/common/common.py
@@ -1,3 +1,65 @@
 
 """A place for common utilities between wubloader components"""
 
+
+import datetime
+
+import dateutil.parser
+import yaml
+
+
+class Config(object):
+	def load(self,
+		run_start_time,
+	):
+		self.run_start_time = dateutil.parser.parse(run_start_time)
+
+
+CONF = Config()
+
+
+def load_config(path="/etc/wubloader.yaml"):
+	with open(path) as f:
+		CONF.load(**yaml.safe_load(f))
+
+
+def dt_to_bustime(dt):
+	"""Convert a datetime to bus time. Bus time is seconds since the start of the run
+	as defined in the config file."""
+	return (dt - CONF.run_start_time).total_seconds()
+
+
+def bustime_to_dt(bustime):
+	"""Convert from bus time to a datetime"""
+	return CONF.run_start_time + datetime.timedelta(seconds=bustime)
+
+
+def format_bustime(bustime, round="millisecond"):
+	"""Convert bustime to a human-readable string (-)H:MM:SS.fff, with the
+	ending cut off depending on the value of round:
+		"millisecond": (default) Round to the nearest millisecond.
+		"second": Round down to the current second.
+		"minute": Round down to the current minute.
+	Examples:
+		0:00:00.000
+		1:23:00
+		110:50
+		159:59:59.999
+		-10:30:01.100
+	Note that a negative value only indicates the number of hours after the start
+	is negative, the number of minutes/seconds is simply time past the hour.
+	eg. the bustime "-1:20:00" indicates the run begins in 40 minutes, not 80 minutes.
+	"""
+	whole_secs, fractional = divmod(bustime, 1)
+	total_mins, secs = divmod(whole_secs, 60)
+	hours, mins = divmod(total_mins, 60)
+	parts = "{}:{:02d}:{:02d}:{:.3f}".format(hours, mins, secs, fractional).split(":")
+	if round == "millisecond":
+		pass
+	elif round == "second":
+		parts = parts[:-1]
+	elif round == "minute":
+		parts = parts[:-2]
+	else:
+		raise ValueError("Bad rounding value: {!r}".format(round))
+	return ":".join(parts)
diff --git a/common/setup.py b/common/setup.py
index 1142660..3d173da 100644
--- a/common/setup.py
+++ b/common/setup.py
@@ -5,5 +5,7 @@ setup(
 	version = "0.0.0",
 	py_modules = ["common.py"],
 	install_requires = [
+		"dateutil",
+		"PyYAML<4.0.0",
 	],
 )
diff --git a/config.example.yaml b/config.example.yaml
new file mode 100644
index 0000000..03045aa
--- /dev/null
+++ b/config.example.yaml
@@ -0,0 +1,6 @@
+
+# The timestamp of the beginning of the run.
+# This defines 00:00 bustime.
+# Should be in format YYYY-MM-DD hh:mm:ss.
+# Example: 2018-11-09 18:00:00
+run_start_time: 1970-01-01 00:00:00