diff --git a/lib/nexrad/archive.py b/lib/nexrad/archive.py
index ebd1e32..ea76d34 100644
--- a/lib/nexrad/archive.py
+++ b/lib/nexrad/archive.py
@@ -3,6 +3,14 @@ import re
 
 from nexrad.s3 import S3Bucket
 
+class ArchiveDateError(Exception):
+    def __init__(self, supplied: str, missing: str):
+        self.supplied = supplied
+        self.missing  = missing
+
+    def __str__(self):
+        return "Date {self.supplied} was supplied, but required {self.missing} is missing"
+
 class Archive():
     path:   str
     bucket: S3Bucket
@@ -28,26 +36,44 @@ class Archive():
     RE_CALL      = re.compile(r'^[A-Z]{4}$')
     RE_PRODUCT   = re.compile(r'^([A-Z]{4})(\d{4})(\d{2})(\d{2})_(\d{2})(\d{2})(\d{2})')
 
-    def each_downloaded_key(self):
+    def each_downloaded_key(self,
+                            year:  int=None,
+                            month: int=None,
+                            day:   int=None):
         parts = [self.path]
 
-        for year in os.scandir(os.path.join(*parts)):
-            if not (year.is_dir() and self.RE_YEAR.match(year.name)):
+        if day is not None and month is None:
+            raise ArchiveDateError('day', 'month')
+
+        if month is not None and year is None:
+            raise ArchiveDateError('month', 'year')
+
+        for cur_year in os.scandir(os.path.join(*parts)):
+            if not (cur_year.is_dir() and self.RE_YEAR.match(cur_year.name)):
                 continue
 
-            parts.append(year.name)
+            if year is not None and int(cur_year.name) != year:
+                continue
 
-            for month in os.scandir(os.path.join(*parts)):
-                if not (month.is_dir() and self.RE_MONTH_DAY.match(month.name)):
+            parts.append(cur_year.name)
+
+            for cur_month in os.scandir(os.path.join(*parts)):
+                if not (cur_month.is_dir() and self.RE_MONTH_DAY.match(cur_month.name)):
                     continue
 
-                parts.append(month.name)
+                if month is not None and int(cur_month.name) != month:
+                    continue
 
-                for day in os.scandir(os.path.join(*parts)):
-                    if not (day.is_dir() and self.RE_MONTH_DAY.match(day.name)):
+                parts.append(cur_month.name)
+
+                for cur_day in os.scandir(os.path.join(*parts)):
+                    if not (cur_day.is_dir() and self.RE_MONTH_DAY.match(cur_day.name)):
                         continue
 
-                    parts.append(day.name)
+                    if day is not None and int(cur_day.name) != day:
+                        continue
+
+                    parts.append(cur_day.name)
 
                     for call in os.scandir(os.path.join(*parts)):
                         if not (call.is_dir() and self.RE_CALL.match(call.name)):