diff --git a/__tests__/meta.test.ts b/__tests__/meta.test.ts
index 5b1efff..ad8a2ff 100644
--- a/__tests__/meta.test.ts
+++ b/__tests__/meta.test.ts
@@ -76,6 +76,53 @@ describe('isRawStatement', () => {
   });
 });
 
+describe('global expressions', () => {
+  // prettier-ignore
+  test.each([
+    [
+      'top-level',
+      `type=raw,value=latest,enable={{is_prerelease}}`
+    ],
+    [
+      'param',
+      `type=raw,value={{date is_prerelease}}`
+    ],
+    [
+      'hash value',
+      `type=raw,value={{date 'YYYYMMDD' tz=is_prerelease}}`
+    ],
+    [
+      'subexpression',
+      `type=raw,value={{date (is_prerelease)}}`
+    ],
+    [
+      'block param',
+      `type=raw,value={{#if is_prerelease}}latest{{/if}}`
+    ],
+    [
+      'nested program',
+      `type=raw,value={{#is_default_branch}}{{is_prerelease}}{{/is_default_branch}}`
+    ],
+  ])('throws for unknown global expression as %s', async (_name: string, tag: string) => {
+    process.env = dotenv.parse(fs.readFileSync(path.join(__dirname, 'fixtures', 'event_push_master.env')));
+    const toolkit = new Toolkit();
+    const repo = await toolkit.github.repoData();
+    const context = await getContext(ContextSource.workflow, toolkit);
+
+    expect(() => {
+      new Meta(
+        {
+          ...getInputs(),
+          images: ['user/app'],
+          tags: [tag]
+        },
+        context,
+        repo
+      );
+    }).toThrow('{{is_prerelease}} is not a valid global expression');
+  });
+});
+
 const tagsLabelsTest = async (name: string, envFile: string, inputs: Inputs, exVersion: Version, exTags: Array<string>, exLabels: Array<string>, exAnnotations: Array<string> | undefined) => {
   process.env = dotenv.parse(fs.readFileSync(path.join(__dirname, 'fixtures', envFile)));
   const toolkit = new Toolkit();
@@ -2760,16 +2807,16 @@ describe('pr', () => {
       {
         images: ['org/app'],
         tags: [
-          `type=raw,value={{commit_date YYYY-MM-DD-HHmmSS}}`,
+          `type=raw,value={{commit_date 'YYYY-MM-DD-HHmmSS'}}`,
         ]
       } as Inputs,
       {
-        main: "2020-01-10T00-30-00Z",
+        main: "2020-01-10-003000",
         partial: [],
         latest: false
       } as Version,
       [
-        'org/app:2020-01-10T00-30-00Z'
+        'org/app:2020-01-10-003000'
       ],
       [
         "org.opencontainers.image.created=2020-01-10T00:30:00.000Z",
@@ -2779,7 +2826,7 @@ describe('pr', () => {
         "org.opencontainers.image.source=https://github.com/octocat/Hello-World",
         "org.opencontainers.image.title=Hello-World",
         "org.opencontainers.image.url=https://github.com/octocat/Hello-World",
-        "org.opencontainers.image.version=2020-01-10T00-30-00Z"
+        "org.opencontainers.image.version=2020-01-10-003000"
       ],
       undefined
     ],
@@ -3136,16 +3183,16 @@ describe('pr-head-sha', () => {
       {
         images: ['org/app'],
         tags: [
-          `type=raw,value=src-{{commit_date YYYY-MM-DD}}`,
+          `type=raw,value=src-{{commit_date 'YYYY-MM-DD'}}`,
         ]
       } as Inputs,
       {
-        main: "src-2020-01-10T00-30-00Z",
+        main: "src-2020-01-10",
         partial: [],
         latest: false
       } as Version,
       [
-        "org/app:src-2020-01-10T00-30-00Z",
+        "org/app:src-2020-01-10",
       ],
       [
         "org.opencontainers.image.created=2020-01-10T00:30:00.000Z",
@@ -3155,7 +3202,7 @@ describe('pr-head-sha', () => {
         "org.opencontainers.image.source=https://github.com/octocat/Hello-World",
         "org.opencontainers.image.title=Hello-World",
         "org.opencontainers.image.url=https://github.com/octocat/Hello-World",
-        "org.opencontainers.image.version=src-2020-01-10T00-30-00Z",
+        "org.opencontainers.image.version=src-2020-01-10",
       ]
     ],
   ])('given %o with %o event', async (name: string, envFile: string, inputs: Inputs, exVersion: Version, exTags: Array<string>, exLabelsAnnotations: Array<string>) => {
diff --git a/src/meta.ts b/src/meta.ts
index 33c0d3e..6a86a28 100644
--- a/src/meta.ts
+++ b/src/meta.ts
@@ -400,7 +400,7 @@ export class Meta {
     const context = this.context;
     const currentDate = this.date;
     const commitDate = this.context.commitDate;
-    return handlebars.compile(val)({
+    const globalExp = {
       branch: function () {
         if (!/^refs\/heads\//.test(context.ref)) {
           return '';
@@ -480,7 +480,60 @@ export class Meta {
         });
         return m.tz(tz).format(format);
       }
-    });
+    };
+    const expressions = Object.keys(globalExp);
+    const template = handlebars.parseWithoutProcessing(val);
+    const nodes: unknown[] = [...template.body];
+    for (const node of nodes) {
+      if (node == undefined || typeof node !== 'object') {
+        continue;
+      }
+      const statement = node as Record<string, unknown>;
+      switch (statement.type) {
+        case 'ContentStatement':
+        case 'CommentStatement':
+        case 'StringLiteral':
+        case 'BooleanLiteral':
+        case 'NumberLiteral':
+        case 'UndefinedLiteral':
+        case 'NullLiteral': {
+          break;
+        }
+        case 'Program': {
+          nodes.push(...((statement.body as unknown[] | undefined) || []));
+          break;
+        }
+        case 'Hash': {
+          nodes.push(...((statement.pairs as unknown[] | undefined) || []));
+          break;
+        }
+        case 'HashPair': {
+          nodes.push(statement.value);
+          break;
+        }
+        case 'MustacheStatement':
+        case 'Decorator':
+        case 'SubExpression':
+        case 'BlockStatement':
+        case 'DecoratorBlock': {
+          nodes.push(...((statement.params as unknown[] | undefined) || []), statement.hash, statement.program, statement.inverse, statement.path);
+          break;
+        }
+        case 'PartialStatement':
+        case 'PartialBlockStatement': {
+          nodes.push(...((statement.params as unknown[] | undefined) || []), statement.hash, statement.program, statement.name);
+          break;
+        }
+        case 'PathExpression': {
+          const expression = statement.original;
+          if (typeof expression == 'string' && !expressions.includes(expression)) {
+            throw new Error(`{{${expression}}} is not a valid global expression`);
+          }
+          break;
+        }
+      }
+    }
+    return handlebars.compile(val)(globalExp);
   }
 
   private getImageNames(): Array<string> {