diff -r fec01f044474 -r ef0fc9ad30c1 core/src/luan/modules/IoLuan.java
--- a/core/src/luan/modules/IoLuan.java	Mon Aug 01 01:44:39 2016 -0600
+++ b/core/src/luan/modules/IoLuan.java	Sun Aug 07 21:03:14 2016 -0600
@@ -520,6 +520,11 @@
 			}
 		}
 
+		public void set_last_modified(long time) throws LuanException {
+			if( !file.setLastModified(time) )
+				throw new LuanException("couldn't set_last_modified on "+file);
+		}
+
 		@Override public LuanTable table() {
 			LuanTable tbl = super.table();
 			try {
@@ -544,6 +549,9 @@
 				tbl.rawPut( "last_modified", new LuanJavaFunction(
 					File.class.getMethod( "lastModified" ), file
 				) );
+				tbl.rawPut( "set_last_modified", new LuanJavaFunction(
+					LuanFile.class.getMethod( "set_last_modified", Long.TYPE ), this
+				) );
 				tbl.rawPut( "length", new LuanJavaFunction(
 					File.class.getMethod( "length" ), file
 				) );