diff --git a/src/core/zip.js b/src/core/zip.js
new file mode 100644
index 0000000..71cbcc8
--- /dev/null
+++ b/src/core/zip.js
@@ -0,0 +1,179 @@
+import fs from 'fs';
+import zlib from 'zlib';
+
+const METHOD_STORE = 0;
+const METHOD_DEFLATE = 8;
+
+/**
+ * convert a JS Date to DOS date/time fields used by the zip format
+ */
+function dosDateTime(date) {
+    const time = ((date.getHours() & 0x1f) << 11) | ((date.getMinutes() & 0x3f) << 5) | ((date.getSeconds() >> 1) & 0x1f);
+    const day = (((Math.max(date.getFullYear(), 1980) - 1980) & 0x7f) << 9) | (((date.getMonth() + 1) & 0xf) << 5) | (date.getDate() & 0x1f);
+
+    return {time, day};
+}
+
+/**
+ * reverse of dosDateTime
+ */
+function dosToDate(day, time) {
+    const year = ((day >> 9) & 0x7f) + 1980;
+    const month = ((day >> 5) & 0xf) - 1;
+    const date = day & 0x1f;
+    const hours = (time >> 11) & 0x1f;
+    const minutes = (time >> 5) & 0x3f;
+    const seconds = (time & 0x1f) * 2;
+
+    return new Date(year, month, date, hours, minutes, seconds);
+}
+
+/**
+ * minimal zip (deflate) writer, so archiving does not require
+ * an external dependency.
+ */
+class Zip {
+    constructor() {
+        this.entries = [];
+    }
+
+    /**
+     * add a file to the archive
+     * @param name path of the file inside the archive, e.g. "01/abc.json"
+     * @param data Buffer with the file's contents
+     * @param date last modified date of the entry
+     */
+    addFile(name, data, date = new Date()) {
+        const compressed = zlib.deflateRawSync(data);
+        const useCompressed = compressed.length < data.length;
+
+        this.entries.push({
+            name,
+            data,
+            payload: useCompressed ? compressed : data,
+            method: useCompressed ? METHOD_DEFLATE : METHOD_STORE,
+            crc: zlib.crc32(data),
+            date
+        });
+
+        return this;
+    }
+
+    /**
+     * build the zip file as a Buffer
+     * @returns {Buffer}
+     */
+    toBuffer() {
+        const localParts = [];
+        const centralParts = [];
+        let offset = 0;
+
+        for (const entry of this.entries) {
+            const nameBuf = Buffer.from(entry.name, 'utf8');
+            const {time, day} = dosDateTime(entry.date);
+
+            const localHeader = Buffer.alloc(30);
+            localHeader.writeUInt32LE(0x04034b50, 0);
+            localHeader.writeUInt16LE(20, 4);
+            localHeader.writeUInt16LE(0x0800, 6);
+            localHeader.writeUInt16LE(entry.method, 8);
+            localHeader.writeUInt16LE(time, 10);
+            localHeader.writeUInt16LE(day, 12);
+            localHeader.writeUInt32LE(entry.crc, 14);
+            localHeader.writeUInt32LE(entry.payload.length, 18);
+            localHeader.writeUInt32LE(entry.data.length, 22);
+            localHeader.writeUInt16LE(nameBuf.length, 26);
+            localHeader.writeUInt16LE(0, 28);
+
+            localParts.push(localHeader, nameBuf, entry.payload);
+
+            const centralHeader = Buffer.alloc(46);
+            centralHeader.writeUInt32LE(0x02014b50, 0);
+            centralHeader.writeUInt16LE(20, 4);
+            centralHeader.writeUInt16LE(20, 6);
+            centralHeader.writeUInt16LE(0x0800, 8);
+            centralHeader.writeUInt16LE(entry.method, 10);
+            centralHeader.writeUInt16LE(time, 12);
+            centralHeader.writeUInt16LE(day, 14);
+            centralHeader.writeUInt32LE(entry.crc, 16);
+            centralHeader.writeUInt32LE(entry.payload.length, 20);
+            centralHeader.writeUInt32LE(entry.data.length, 24);
+            centralHeader.writeUInt16LE(nameBuf.length, 28);
+            centralHeader.writeUInt16LE(0, 30);
+            centralHeader.writeUInt16LE(0, 32);
+            centralHeader.writeUInt16LE(0, 34);
+            centralHeader.writeUInt32LE(0, 38);
+            centralHeader.writeUInt32LE(offset, 42);
+
+            centralParts.push(centralHeader, nameBuf);
+
+            offset += localHeader.length + nameBuf.length + entry.payload.length;
+        }
+
+        const centralSize = centralParts.reduce((n, b) => n + b.length, 0);
+        const centralOffset = offset;
+
+        const end = Buffer.alloc(22);
+        end.writeUInt32LE(0x06054b50, 0);
+        end.writeUInt16LE(0, 4);
+        end.writeUInt16LE(0, 6);
+        end.writeUInt16LE(this.entries.length, 8);
+        end.writeUInt16LE(this.entries.length, 10);
+        end.writeUInt32LE(centralSize, 12);
+        end.writeUInt32LE(centralOffset, 16);
+        end.writeUInt16LE(0, 20);
+
+        return Buffer.concat([...localParts, ...centralParts, end]);
+    }
+
+    /**
+     * write the zip archive to disk atomically
+     * @param file
+     */
+    write(file) {
+        const tmpFile = `${file}.tmp`;
+
+        fs.writeFileSync(tmpFile, this.toBuffer());
+        fs.renameSync(tmpFile, file);
+    }
+
+    /**
+     * read an existing zip archive (as produced by this class) back into
+     * a Zip instance, so new files can be appended to it. Returns an
+     * empty Zip if the file does not exist.
+     * @param file
+     * @returns {Zip}
+     */
+    static fromFile(file) {
+        const zip = new Zip();
+
+        if (!fs.existsSync(file)) return zip;
+
+        const buffer = fs.readFileSync(file);
+        let offset = 0;
+
+        while (offset < buffer.length && buffer.readUInt32LE(offset) === 0x04034b50) {
+            const method = buffer.readUInt16LE(offset + 8);
+            const time = buffer.readUInt16LE(offset + 10);
+            const day = buffer.readUInt16LE(offset + 12);
+            const crc = buffer.readUInt32LE(offset + 14);
+            const compressedSize = buffer.readUInt32LE(offset + 18);
+            const nameLength = buffer.readUInt16LE(offset + 26);
+            const extraLength = buffer.readUInt16LE(offset + 28);
+
+            const nameStart = offset + 30;
+            const name = buffer.toString('utf8', nameStart, nameStart + nameLength);
+            const dataStart = nameStart + nameLength + extraLength;
+            const payload = buffer.subarray(dataStart, dataStart + compressedSize);
+            const data = method === METHOD_DEFLATE ? zlib.inflateRawSync(payload) : Buffer.from(payload);
+
+            zip.entries.push({name, data, payload: Buffer.from(payload), method, crc, date: dosToDate(day, time)});
+
+            offset = dataStart + compressedSize;
+        }
+
+        return zip;
+    }
+}
+
+export default Zip;
diff --git a/src/gtt.js b/src/gtt.js
index cd2a84c..70805d0 100755
--- a/src/gtt.js
+++ b/src/gtt.js
@@ -16,6 +16,7 @@ import log from './timekeeping/commands/log.js';
 import sync from './timekeeping/commands/sync.js';
 import edit from './timekeeping/commands/edit.js';
 import delCmd from './timekeeping/commands/delete.js';
+import archive from './timekeeping/commands/archive.js';
 import report from './reporting/commands/report.js';
 
 program
@@ -31,6 +32,7 @@ program
     .addCommand(sync())
     .addCommand(edit())
     .addCommand(delCmd())
+    .addCommand(archive())
     .addCommand(report())
     .addCommand(config())
     .parse(process.argv);
diff --git a/src/timekeeping/commands/archive.js b/src/timekeeping/commands/archive.js
new file mode 100644
index 0000000..a7b2c9d
--- /dev/null
+++ b/src/timekeeping/commands/archive.js
@@ -0,0 +1,55 @@
+import fs from 'fs';
+import {Command} from 'commander';
+import Config from '../../core/file-config.js';
+import Cli from '../../core/cli.js';
+import Fs from '../../core/filesystem.js';
+import Zip from '../../core/zip.js';
+import Timekeeper from '../timekeeper.js';
+
+function archive() {
+    const archive = new Command('archive', 'archive synced time records into yearly zip files (filesYYYY.zip), one folder per month')
+        .option('--year <year>', 'only archive the given year')
+        .option('--verbose', 'show verbose output')
+        .action((options, program) => {
+
+Cli.verbose = program.opts().verbose;
+
+let config = new Config(process.cwd()),
+    timekeeper = new Timekeeper(config),
+    year = program.opts().year;
+
+timekeeper.archiveInit()
+    .then(grouped => {
+        let years = year ? Object.keys(grouped).filter(y => y === year) : Object.keys(grouped);
+
+        if (years.length === 0) {
+            console.log('Nothing to archive.');
+            return;
+        }
+
+        years.forEach(archiveYear => {
+            let file = Fs.join(config.frameDir, `files${archiveYear}.zip`),
+                zip = Zip.fromFile(file),
+                frames = [];
+
+            Object.keys(grouped[archiveYear]).forEach(month => {
+                grouped[archiveYear][month].forEach(frame => {
+                    zip.addFile(`${month}/${frame.id}.json`, fs.readFileSync(frame.file), frame.date.toDate());
+                    frames.push(frame);
+                });
+            });
+
+            zip.write(file);
+            frames.forEach(frame => Fs.remove(frame.file));
+
+            console.log(`Archived ${frames.length} record(s) into ${file}`);
+        });
+    })
+    .catch(error => Cli.error(error));
+
+}
+);
+return archive;
+}
+
+export default archive;
diff --git a/src/timekeeping/timekeeper.js b/src/timekeeping/timekeeper.js
index 4446001..2efebcb 100755
--- a/src/timekeeping/timekeeper.js
+++ b/src/timekeeping/timekeeper.js
@@ -49,6 +49,36 @@ class Timekeeper {
         this.sync.frames.filter(frame => !(Math.ceil(frame.duration) === frame.notes.reduce((n, m) => (n + m.time), 0)));
     }
 
+    /**
+     * Group all finished, synced frames by year and month (based on
+     * start time), for archiving. Refuses to run while frames are
+     * still waiting to be synced to GitLab.
+     * @returns {Promise<Object>} {year: {month: [frame, ...]}}
+     */
+    async archiveInit() {
+        await this.syncInit();
+
+        if (this.sync.frames.length > 0) {
+            throw new Error('Not all frames are synced yet. Run `gtt sync` first.');
+        }
+
+        let grouped = {};
+
+        await new FrameCollection(this.config).forEach(frame => {
+            if (frame.stop === false) return;
+
+            let year = frame.date.format('YYYY'),
+                month = frame.date.format('MM');
+
+            if (!grouped[year]) grouped[year] = {};
+            if (!grouped[year][month]) grouped[year][month] = [];
+
+            grouped[year][month].push(frame);
+        });
+
+        return grouped;
+    }
+
     /**
      * Resolve merge_requests and issues
      * respectively.