diff --git a/docs/CONFIGURATION.md b/docs/CONFIGURATION.md
index e68daf1..f7a24ff 100644
--- a/docs/CONFIGURATION.md
+++ b/docs/CONFIGURATION.md
@@ -147,6 +147,7 @@ bar {
 | `position`           | enum   | `top`              | Bar position (`top` or `bottom`)              |
 | `vertical_padding`   | u8     | `5`                | Vertical padding above and below text         |
 | `horizontal_padding` | u8     | `5`                | Horizontal padding between bar edges and text |
+| `time_format`        | string | `%Y-%m-%d %H:%M, %A` | strftime format string for the clock display (an empty string hides the clock) |
 
 ### Margins
 
diff --git a/docs/TODO.md b/docs/TODO.md
index 0140a53..d5493b8 100644
--- a/docs/TODO.md
+++ b/docs/TODO.md
@@ -10,7 +10,6 @@ These are in rough order of my priority, though no promises I do them in this or
 - [ ] Support configuring bar item positions (left/center/right)
 - [ ] Support overriding config location
 - [ ] Add support for center-primary layout
-- [ ] Support 12-hour clock format (maybe take any time format string?)
 - [ ] Support per-output bar visibility
 - [ ] Support more window rule options (e.g. ssd/csd)
 - [ ] Support solid `background-color` fallback (no wallpaper)
@@ -50,3 +49,4 @@ These are in rough order of my priority, though no promises I do them in this or
 - [x] Support configuring primary vs secondary stack side
 - [x] Add focused window title to bar
 - [x] Add bar padding to config
+- [x] Support 12-hour clock format (maybe take any time format string?)
diff --git a/examples/config.kdl b/examples/config.kdl
index 8c43c34..2fa5222 100644
--- a/examples/config.kdl
+++ b/examples/config.kdl
@@ -28,6 +28,7 @@ borders {
 // Bar widget; shows the time
 bar {
     position top
+    time_format "%H:%M"
 }
 // Tag overlay widget; shown briefly when switching tags
 // Remove this block to disable the overlay entirely
diff --git a/man/beansprout.5.scd b/man/beansprout.5.scd
index 2c73352..7ac835c 100644
--- a/man/beansprout.5.scd
+++ b/man/beansprout.5.scd
@@ -143,6 +143,11 @@ bar {
 *horizontal_padding* _pixels_
 	Horizontal padding between bar edges and text. (Default: 5)
 
+*time_format* _format_
+	strftime format string for the clock display. Invalid format strings
+	are ignored and the default is used instead. Set to an empty string
+	to hide the clock. (Default: "%Y-%m-%d %H:%M, %A")
+
 The bar also supports *margins* and *anchors* child blocks; see *TAG OVERLAY*
 for their format.
 
diff --git a/src/Bar.zig b/src/Bar.zig
index 98a65e6..682edd2 100644
--- a/src/Bar.zig
+++ b/src/Bar.zig
@@ -7,6 +7,9 @@ const Bar = @This();
 /// Standard base DPI at a scale of 1
 const base_dpi = 96;
 
+/// Default strftime string to use for the clock
+pub const default_time_format = "%Y-%m-%d %H:%M, %A";
+
 context: *Context,
 
 /// The timezone of the computer.
@@ -61,6 +64,9 @@ pub const Options = struct {
     vertical_padding: u8 = 5,
     /// Horizontal padding between bar edges and content, in pixels
     horizontal_padding: u8 = 5,
+
+    /// strftime format string for the clock display
+    time_format: []const u8 = default_time_format,
 };
 
 pub fn init(context: *Context, output: *Output, options: Options) !Bar {
@@ -240,7 +246,7 @@ pub fn draw(bar: *Bar) !void {
     // Convert time to a string
     var time_buf: [255:0]u8 = undefined;
     var time_writer = Io.Writer.fixed(&time_buf);
-    try dt.strftime(&time_writer, "%H:%M");
+    try dt.strftime(&time_writer, options.time_format);
 
     // Convert date string to Unicode codepoints
     const time_codepoints = try utils.utf8ToCodepoints(time_writer.buffered());
diff --git a/src/config/BarConfig.zig b/src/config/BarConfig.zig
index bf20c67..34ebf99 100644
--- a/src/config/BarConfig.zig
+++ b/src/config/BarConfig.zig
@@ -12,6 +12,7 @@ const NodeName = enum {
     vertical_padding,
     horizontal_padding,
     margins,
+    time_format,
 };
 const MarginsNodeName = enum { top, right, bottom, left };
 
@@ -38,6 +39,10 @@ vertical_padding: u8 = 5,
 /// Horizontal padding between bar edges and content, in pixels
 horizontal_padding: u8 = 5,
 
+/// strftime format string for the clock display.
+/// null means use the default.
+time_format: ?[]const u8 = null,
+
 pub fn toBarOptions(config: BarConfig) Bar.Options {
     return .{
         .fonts = config.fonts orelse "monospace:size=14",
@@ -52,6 +57,7 @@ pub fn toBarOptions(config: BarConfig) Bar.Options {
         },
         .vertical_padding = config.vertical_padding,
         .horizontal_padding = config.horizontal_padding,
+        .time_format = config.time_format orelse Bar.default_time_format,
     };
 }
 
@@ -92,7 +98,18 @@ pub fn load(config: *Config, parser: *kdl.Parser, hostname: ?[]const u8) !void {
                                 logWarnInvalidNodeArg(name, val_str);
                             }
                         },
-
+                        .time_format => {
+                            if (node.argcount() < 1) {
+                                logWarnMissingNodeArg(name, "format string");
+                                continue;
+                            }
+                            if (validateTimeFormat(val_str)) {
+                                config.bar_config.?.time_format = utils.gpa.dupe(u8, val_str) catch @panic("Out of memory");
+                                logDebugSettingNode(name, val_str);
+                            } else {
+                                logWarnInvalidNodeArg(name, val_str);
+                            }
+                        },
                         .margins => next_child_block = .margins,
                         inline .background_color,
                         .text_color,
@@ -192,15 +209,26 @@ inline fn logWarnInvalidNodeArg(node_name: anytype, node_value: []const u8) void
     }
 }
 
+fn validateTimeFormat(format: []const u8) bool {
+    // Try formatting with a dummy time to validate the format string
+    var buf: [255]u8 = undefined;
+    var writer = Io.Writer.fixed(&buf);
+    const dummy_time = zeit.Time{};
+    dummy_time.strftime(&writer, format) catch return false;
+    return true;
+}
+
 inline fn logWarnMissingNodeArg(node_name: NodeName, comptime arg: []const u8) void {
     log.warn("\"bar.{s}\" missing " ++ arg ++ " argument. Ignoring", .{@tagName(node_name)});
 }
 
 const std = @import("std");
 const fmt = std.fmt;
+const Io = std.Io;
 
 const kdl = @import("kdl");
 const pixman = @import("pixman");
+const zeit = @import("zeit");
 
 const utils = @import("../utils.zig");
 const Bar = @import("../Bar.zig");
diff --git a/src/main.zig b/src/main.zig
index 4191091..ba9eceb 100644
--- a/src/main.zig
+++ b/src/main.zig
@@ -129,19 +129,17 @@ fn run(wl_display: *wl.Display, context: *Context) !void {
             fatal("wl_display flush failed: E{s}", .{@tagName(errno)});
         }
 
-        // Get the number of milliseconds to the top of the next minute
-        const time = std.time.timestamp();
-        if (time < 0) {
-            log.err("Got a negative time ({d})", .{time});
-            return error.InvalidTime;
-        }
-        const timeout: i32 = @intCast((@divFloor(time, 60) * 60 + 60 - time) * 1000);
+        // Get the number of milliseconds to the top of the next second
+        const time_ns = std.time.nanoTimestamp();
+        const ns_per_sec = std.time.ns_per_s;
+        const remainder_ns = @mod(time_ns, ns_per_sec);
+        const timeout: i32 = @intCast(@divFloor(ns_per_sec - remainder_ns, std.time.ns_per_ms));
 
         const poll_rc = posix.poll(&pollfds, timeout) catch |err| {
             fatal("Failed to poll {s}", .{@errorName(err)});
         };
         if (poll_rc == 0) {
-            // If poll returns 0, it timed out, meaning we hit the top of the minute
+            // If poll returns 0, it timed out, meaning we hit the top of the next second
             // and need to update the clock.
             var it = context.wm.outputs.iterator(.forward);
             while (it.next()) |output| {