diff --git a/node/logger.js b/node/logger.js
new file mode 100644
index 0000000..006879d
--- /dev/null
+++ b/node/logger.js
@@ -0,0 +1,16 @@
+const LEVELS = ["debug", "info", "warn", "error"];
+
+export function createLogger(minLevel = "info") {
+  const threshold = LEVELS.indexOf(minLevel);
+  if (threshold === -1) {
+    throw new RangeError(`unknown level: ${minLevel}`);
+  }
+  return LEVELS.reduce((logger, level, index) => {
+    logger[level] = (message) => {
+      if (index >= threshold) {
+        console.log(`[${level.toUpperCase()}] ${message}`);
+      }
+    };
+    return logger;
+  }, {});
+}
diff --git a/python/dates.py b/python/dates.py
new file mode 100644
index 0000000..c68cdda
--- /dev/null
+++ b/python/dates.py
@@ -0,0 +1,21 @@
+from datetime import date, timedelta
+
+
+def days_between(start, end):
+    if end < start:
+        raise ValueError("end must not precede start")
+    return (end - start).days
+
+
+def add_business_days(start, count):
+    current = start
+    remaining = count
+    while remaining > 0:
+        current += timedelta(days=1)
+        if current.weekday() < 5:
+            remaining -= 1
+    return current
+
+
+def is_weekend(value):
+    return value.weekday() >= 5